Activation of multiple xDSL modems with implicit channel probe

ABSTRACT

Apparatus and method for establishing a communication link. A negotiation data transmitting section, associated with an initiating communication device, transmits carriers to a responding communication device. A negotiation data receiving section, associated with the plurality of initiating communication devices, receives carriers from the responding communication device, in response to the transmitted carriers. A selecting device selects an appropriate communication device from the plurality of communication devices, in accordance with the responding communication device, in order to establish a communication channel.

This application claims the benefit of U.S. Provisional Application No.60/080,310 filed on Apr. 1, 1998, U.S. Provisional Application No.60/089,850 filed on Jun. 19, 1998, U.S. Provisional Application No.60/093,669 filed on Jul. 22, 1998; and U.S. Provisional Application No.60/094,479, filed on Jul. 29, 1998.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is directed to a communications device, such as,for example, a modem, and a method for enabling data communication, andin particular, to an apparatus and method that detects variouscommunication configurations and selects an appropriate communicationconfiguration to establish a communication link.

2. Discussion of Background and other Information

Traditionally, data communication devices, such as, for example, modems(both analog and digital), have been employed over public switchedtelephone networks (PSTN) to transmit data between a first location anda second location. Such modems typically operate within a conventionalvoice band (e.g., approximately 0 through 4 kHz bandwidth) of the PSTN.Early modems transmitted data over the PSTN at a speed of approximately300 bit/second, or less. Over time, and with the increased popularity ofthe Internet, faster communication schemes (e.g., modems) were demandedand developed. Currently, the fastest analog modem available (referredto as an ITU-T V.34 modem, as defined by the InternationalTelecommunication Union Telecommunication Standardization Sector(ITU-T)), transmits data at a rate of approximately 33,600 bits/secondunder ideal conditions. Hybrid digital-analog modems, referred to asITU-T V.90 modems, can achieve data transmission rates up to 56,000bits/second under ideal conditions. These modems continue to exchangedata within the approximate 4 kHz bandwidth of the PSTN.

It is not uncommon to transfer data files that are several megabytes(MB) in size. A modem that operates utilizing the V.34 modulationrequires a long time to transfer such a file. As a result, a need hasdeveloped for even faster modems and Internet access methods.

Accordingly, many new communication methods are being proposed and/ordeveloped to transmit high speed or broadband data on the local twistedwire pair that uses the spectrum above the traditional 4 kHz band. Forexample, various “flavors” (variations) of digital subscriber line (DSL)modems have been/are being developed, such as, but not limited to, forexample, DSL, ADSL, VDSL, HDSL, SHDSL and SDSL (the collection of whichis generally referred to as xDSL).

Each xDSL variation employs a different communication scheme, resultingin different upstream and/or downstream transfer speeds, and utilizesdiffering frequency bands of a twisted pair communication channel. Awide range of physical and environmental limitations of the variousconfigurations of the twisted pair wires leads to widely varyingexpectations of a feasible communication capability bandwidth. Dependingon, for example, the quality of the twisted wire pair (e.g., CAT3 wirevs. CAT5 wire), a given xDSL scheme may not be able to transmit data atits maximum advertised data transfer rate.

While xDSL technologies exist and offer the promise of solving the highspeed data transfer problem, several obstacles exist to the rapiddeployment and activation of xDSL equipment.

Several of the various xDSL schemes permit simultaneous communication ona single twisted pair in the voice band and in a frequency band abovethe voice band. To achieve a simultaneous voice band and above voiceband communication, some xDSL variations require filters, including lowpass filters, high pass filters and combinations of filters that aresometimes referred to as “splitters”. The filters separate the frequencyband that carries voice band communication from the frequency band abovethe voice band carrying data communication. The use and type of filtersmay differ between installations.

Recently, there has been technology and market motivation to eliminateor reduce the use of those filters. Thus, for a given communicationchannel, the presence and/or type of filter is often unknown. There is aneed for the communication devices to “know” the existence andconfiguration of such filters before initiating a communication method,as such filters impacts which communication methods are viable.

Many different xDSL and high speed access technologies solutions havebeen described in public, proprietary, and/or de facto standards.Equipment at each end of a connection may implement one standard (orseveral standards) that may (or may not) be mutually compatible. Ingeneral, startup and initialization methods of the various standardshave been heretofore incompatible.

Line environments surrounding the xDSL data communication schemes, suchas, for example, their ability to co-exist with a conventional analogmodem that communicates within the conventional voice band (e.g., 0-4kHz bandwidth), differences in central office equipment, the quality ofthe line, etc., are numerous, differ significantly, and are complicated.Accordingly, it is essential to be able to determine the capabilities ofthe communication channel, in addition to being able to determine thecapabilities of the communication equipment, in order to establish anoptimum and non-interfering communication link.

User applications can have a wide range of data bandwidth requirements.Although a user could always use the highest capacity xDSL standardcontained in a multiple xDSL box, in general, that will be the mostexpensive service, since communication costs are generally related tothe available bandwidth. When a low bandwidth application is used, theuser may desire the ability to indicate a preference for a low bandwidthxDSL (and hence, a cheaper communication service), as opposed to using ahigh bandwidth xDSL service. As a result, it is desirable to have asystem that automatically indicates user service and applicationrequirements to the other end of the link (e.g., central office).

In addition to the physical composition of the communication equipmentand communication channel, high speed data access complexity is alsoinfluenced by regulatory issues. The result has been that possibleconfiguration combinations at each end of a communication channel havegrown exponentially.

The US Telecommunication Act of 1996 has opened the vast infrastructureof metallic twisted wire pairs to both competitive (CLEC) usage, and theincumbent telephone provider (ILEC) that originally installed the wires.Thus, multiple providers may have differing responsibilities andequipment deployed for a single wire pair.

In a given central office termination, a given communication channel(line) may be solely provisioned for voiceband-only, ISDN, or one of themany new xDSL (ADSL, VDSL, HDSL, SDSL, etc.) services. Since theCarterphone court decision, telephone service users (customers) have awide range of freedom for placing (i.e., installing and utilizing)communication customer premise equipment (e.g., telephones, answeringmachines, modems, etc.) on voiceband channels. However, customer premiseequipment (CPE) associated with leased data circuits has typically beenfurnished by the service provider. As the high speed communicationmarket continues to evolve, customers will also expect and demandfreedom in selecting and providing their own CPE for high speed circuitsusing the band above the traditional voice band. This will placeincreased pressure on the service providers to be prepared for a widerange of equipment to be unexpectedly connected to a given line.

The customer premise wiring condition/configuration inside of thecustomer premise (e.g. home, office, etc.) and the range of devicesalready attached to nodes in the wiring are varied and unspecifiable.For a service provider to dispatch a technician and/or craftsman toanalyze the premise wiring and/or make an installation represents alarge cost. Accordingly, an efficient and inexpensive (i.e., non-humanintervention) method is needed to provide for the initialization ofcircuits in the situation where a plethora of communication methods andconfiguration methods exist.

Still further, switching equipment may exist between the communicationchannel termination and the actual communication device. That switchingequipment may function to direct a given line to a given type ofcommunication device.

Thus, a high speed data access start-up technique (apparatus and method)that solves the various equipment, communication channel, and regulatoryenvironment problems is urgently needed.

In the past, the ITU-T has published recommended methods for initiatingdata communication over voice band channels. Specifically, twoRecommendations were produced:

1) Recommendation V.8 (09/94)—“Procedures for Starting Sessions of DataTransmission over the General Switched Telephone Network”; and

2) Recommendation V.8bis (08/96)—“Procedures for the Identification andSelection of Common Modes of Operation Between Data Circuit-terminatingEquipments (DCEs) and Between Data Terminal Equipments (DTEs) over theGeneral Switched Telephone Network”.

Both Recommendations use a sequence of bits transmitted from each modemto identify and negotiate mutually common (shared) operating modes, suchas the modulation scheme employed, protocol, etc. However, both startupsequence Recommendations are applicable only to the conventional voiceband communication methods. Further, these conventional startupsequences do not test (and/or indicate) the constitution and/orcondition of the communication channel between the modems.

However, line condition information, such as, for example, frequencycharacteristics, noise characteristics, presence or absence of asplitter, etc., is useful at the time that plural xDSL modems arenegotiating a connection, prior to actually connecting to each other, ifthe communications link is to be successfully established.

Voice band line probing techniques are known in the art and can be usedto determine voice band line condition information. Such techniques havebeen used to optimize a given modulation method, such as, for example,V.34, but have not been used to optimize startup methods and/orcommunication selection methods. In a set of devices with multiplemodulation methods, V.8 or V.8bis has been used to negotiate and thenselect a particular modulation. After the modulation initiation sequencehas started, line probing techniques are used to receive some indicationof the condition of the communication channel. If it is determined atthat point that a given communication channel can not effectivelysupport a chosen modulation method, time consuming heuristic (i.e.,self-learning) fallback techniques are employed by the prior art to tryand find a modulation method that works.

In order to establish an improved communication link, a method isrequired that observes (examines) the line conditions before attemptingto select the most appropriate communication method. While techniqueshave been established to increase the data rate for a given modulation,the prior art does not provide a method for using channel information toaid in the selection of the communication method.

Unfortunately, in the current state of the art, capability negotiationsoccur without knowledge of the prevailing channel configuration.Explicit knowledge of spectrum, splitting, etc. is vital to theselection of the most appropriate communication mechanism (modulation)decision process.

Definitions

During the following discussion, the following definitions are employed:

activating station (calling station)—the DTE, DCE and other associatedterminal equipment which originates an activation of an xDSL service;

answering station—the DTE, DCE and other associated terminal equipmentwhich answers a call placed on a GSTN;

carrier set—a set of one or more frequencies associated with a PSD maskof a particular xDSL Recommendation;

CAT3—cabling and cabling componenets designed and tested to transmitcleanly to 16 MHZ of communications. Used for voice and data/LAN trafficto 10 megabits per second;

CAT5—cabling and cabling componenets designed and tested to transmitcleanly to 100 MHZ of communications;

communication method—form of communication sometimes referred to asmodems, modulations, line codes, etc.;

downstream—direction of transmission from the xTU-C to the xTU-R;

errored frame—frame that contains a frame check sequence (FCS) error;

Galf—an octet having the value 81₁₆; i.e., the ones complement of anHDLC flag;

initiating signal—signal which initiates a startup procedure;

initiating station—DTE, DCE and other associated terminal equipmentwhich initiates a startup procedure;

invalid frame—frame that has fewer than four octets between flags,excluding transparency octets;

message—framed information conveyed via modulated transmission;

metallic local loop—communication channel 5, the metallic wires thatform the local loop to the customer premise;

responding signal—signal sent in response to an initiating signal;

responding station—station that responds to initiation of acommunication transaction from the remote station;

session—active communications connection, measured from beginning toend,

between computers or applications over a network;

signal—information conveyed via tone based transmission;

signaling family—group of carrier sets which are integral multiples of agiven carrier spacing frequency;

splitter—combination of a high pass filter and a low pass filterdesigned to split a metallic local loop into two bands of operation;

telephony mode—operational mode in which voice or other audio (ratherthan modulated information-bearing messages) is selected as the methodof communication;

transaction—sequence of messages, ending with either a positiveacknowledgment [ACK(1)], a negative acknowledgment (NAK), or a time-out;

terminal—station; and

upstream: The direction of transmission from the xTU-R to the xTU-C.

Abbreviations

The following abbreviations are used throughout the detailed discussion:

ACK—Acknowledge Message;

ADSL—Asymmetric Digital Subscriber Line;

ANS—V.25 answer tone;

ANSam—V.8 modulated answer tone;

AOM—Administration, Operations, and Management;

CCITT—International Telegraph and Telephone Consultative Committee;

CDSL—Consumer Digital Subscriber Line;

CR—Capabilities Request;

CL—Capabilities List;

CLR—Capabilities List Request;

DCME—Digital Circuit Multiplexing Equipment;

DPSK—Differential encoded binary Phase Shift Keying;

DIS—Digital Identification Signal;

DMT—Discrete Multi-Tone;

DSL—Digital Subscriber Line;

EC—Echo canceling;

EOC—Embedded Operations channel;

ES—Escape Signal;

FCS—Frame Check Sequence;

FDM—Frequency Division Multiplexing;

FSK—Frequency Shift Keying;

GSTN—General Switched Telephone Network (same as PSTN);

HDSL—High level Data Link Control;

HSTU—Handshake Transceiver Unit;

IETF—Internet Engineering Task Force;

ISO—International Organization for Standardization;

ITU-T—International Telecommunication Union—TelecommunicationStandardization Sector;

LSB—Least Significant Bit;

LTU—Line Termination Unit (Central office end);

MR—Mode Request;

MS—Mode Select;

MSB—Most Significant Bit;

NAK—Negative Acknowledge Message;

NTU—Network Termination Unit (Customer premise end);

OGM—Outgoing Message (recorded voice or other audio);

ONU—optical network Unit;

POTS—Plain Old Telephone Service

PSD—Power Spectral Density;

PSTN—Public Switched Telephone Network;

RADSL—Rate Adaptive DSL;

REQ—Request Message Type Message;

RFC—Request For Comment;

RTU—RADSL Terminal Unit;

SAVD—Simultaneous or Alternating Voice and Data;

SNR—Signal to Noise Ratio;

VDSL—very high speed Digital Subscriber Line;

xDSL—any of the various types of Digital Subscriber Lines (DSL);

xTU-C—central terminal unit of an xDSL; and

xTU-R—remote terminal unit of an xDSL.

SUMMARY OF THE INVENTION

Based on the foregoing, the present invention is directed to acommunication method, modem device and data communication system thatdetects various configurations, capabilities and limitations of acommunication channel, associated equipment, and regulatory environmentin order to determine a specific (xDSL) communication standardappropriate for the existing line conditions. To accomplish this goal,the invention employs several individual techniques as a system.

According to one aspect of the present invention, a method and apparatusare provided to negotiate between modems that embody multiple (plural)communication methods (e.g., DSL standards), so as to select a singlecommon communication standard to be used for a communication session. Acommunication control section executes a handshake procedure (protocol)in a negotiation channel to obtain information concerning high speeddata communication, including type identification information of thexDSL used in the communication exchange. A communication standard refersto any type of standard, whether defacto, proprietary, or issued by anindustry or governmental body.

According to another aspect of the instant invention, characteristics ofthe communication channel between a central communication system and aremote communication system are determined using an examination signal.The examination signal detects impairments, such as, but not limited to,for example, frequency roll-off and noise, that are identified anddetected between the central system and the remote systems. Informationpertaining to the quality of the communication channel enables thepresent invention to make an informed decision concerning the selectionof a communication standard. (e.g., whether to use CDSL instead of ADSL,or use CDSL instead of VDSL).

The combination of all of the various aspects of the invention providesa method and apparatus for effectively and efficiently performing anaudit of the communication channel and installed equipment to select themost appropriate communication method. System designers, installers, andproviders are able to predetermine and set various parameters that areconsidered by the method and apparatus of the present invention duringthe negotiation process to effectively define the meaning of “mostappropriate means of communication”.

According to the present invention, a procedure to determine a possiblehigh speed communication, and selection of supported capabilities for ahigh speed data communication, and the examination of the communicationline characteristics may be concurrently (simultaneously) executed, thusenabling the immediate shifting to a handshake protocol corresponding tothe determined data communication procedure. In this regard, it isunderstood that the procedure may also be sequentially executed.

The invention may be included in both sides of the communication channelfor optimum negotiation. However, according to an advantage of thepresent invention, the invention can be incorporated into (contained in)just one side of the communication channel. Such configurations will beaccurately reported to the communication systems, and, if appropriate,the communication systems can fall back to legacy (e.g., analog)communication methods, if the communication system provides suchsupport.

The instant invention does not need to be embodied in the actual highspeed communication devices, but may be implemented in intelligentswitches that terminate and/or segment the communication channel. Thisallows a communication system to use various communication standardsimplemented in separate devices (or modems) that can be correctlyassigned (on a “as needed” basis) through explicit negotiation of thecapabilities and requirements of the central system and the remotecommunication system.

According to an advantage of the present invention, an environmentallyfriendly method for selecting start-up carriers is provided.

According to another feature of the present invention, ITU-T G.997.1 maybe used to configure the information field registers.

According to another advantage of the instant invention, a unique dataformat, coding format and data structures for messages is provided.

According to an object of the instant invention, an apparatus forestablishing a communication link, comprises a negotiation datatransmitting section, associated with a plurality of initiatingcommunication devices, that transmits carriers to a respondingcommunication device, a negotiation data receiving section, associatedwith the plurality of initiating communication devices, that receivescarriers from the responding communication device, in response to thetransmitted carriers, and a selecting device that selects an appropriatecommunication device from the plurality of communication devices, inaccordance with the responding communication device, so as to establisha communication channel.

According to a feature of the invention, the transmitted carrierscontain data related to a useable carrier allocation. In addition, thetransmitted carriers and the received carriers may be divided into aplurality of bands. A system selects a plurality of bands to minimizeinterference with a voice band device.

An advantage of the instant invention is that the negotiation datatransmitting section transmits the carriers in accordance withneighboring receiving systems. The transmission characteristics of thetransmitted carriers are re-configurable during a transmission operationin order to minimize interference with the neighboring receivingstations.

According to an object of the instant invention, a method is disclosedfor establishing a communication link. The method transmitspredetermined carriers to a responding communication device, receivespredetermined carriers from the responding communication device, inresponse to the predetermined transmitted carriers, and selects anappropriate communication device from a plurality of communicationdevices, in accordance with the received predetermined carriers, toestablish a communication channel.

A feature of this object of the invention includes the dividing of thetransmitted carriers and the received carriers into a plurality ofbands.

Another feature of this invention is that the transmitting ofpredetermined carriers comprises transmitting the carriers in accordancewith neighboring receiving systems. The transmitting of transmissioncharacteristics of the carriers comprises re-configuring the carriersduring a transmission operation in order to minimize interference withthe neighboring receiving stations.

Another object of the instant invention is to provide a communicationdevice that at least one of transmits and receives a communicationsignal, comprising a data exchanging device that exchanges data, betweenan initiating communicating device and a responding communicationdevice, over a communication channel, and an implicit channel probedevice that analyzes the exchanged data to assess characteristics of thecommunication channel.

The data exchanging device of this invention comprises a transmitterthat transmits results of the analyzed exchanged data as part of theexchanged data.

The implicit channel probe device comprises an analyzer that monitorsthe communication channel by performing a spectral analysis of theexchanged data. The exchange of data and the analysis of exchanged datamay occur at substantially the same time, or sequentially in time.

According to a feature of the invention, the exchanged data comprises aplurality of initializing carriers, the plurality of initializingcarriers being exchanged between the initiating communicating device andthe responding communication device.

According to another object of the instant invention, method for atleast one of transmitting and receiving a communication signal isdisclosed, comprising the exchange of data between an initiatingcommunicating device and a responding communication device, over acommunication channel, and the performing of an implicit channel probeanalysis on the exchanged data to assess characteristics of thecommunication channel.

An advantage of this invention is that the exchange of data comprisestransmitting results of the analyzed exchanged data as part of theexchanged data.

Another advantage of the present invention is that the performing of animplicit channel probe analysis comprises performing a spectral analysisof the exchanged data.

According to a feature of the invention, the method further comprisesexchanging the data and performing the analysis at substantially thesame time, or, alternatively, sequentially in time.

A feature of the current invention resides in the exchanging of aplurality of initializing carriers between the initiating communicatingdevice and the responding communication device.

Another object of the instant invention pertains to a communicationdevice, comprising a communication device that initially transmits datawith a multiplicity of carriers; and a carrier determining device thatreduces the multiplicity of carriers transmitted by said communicationdevice to a predetermined number of carriers, in accordance with apredetermined carrier reduction system.

According to a feature oft he instant invention, the predeterminedcarrier reduction system comprises a pair phase reversal system, amodulate carrier system, or a carrier use and request transmit system.

According to another feature of the invention, the carrier determiningdevice comprises a reduction device that reduces the multiplicity ofcarriers to the predetermined number of carriers in order to limit atransmit power during an initialization procedure.

a still further feature of the instant invention pertains to the carrierdetermining device, which comprises a determining device that determinesthe most usable communications channels.

According to this invention, the initial transmission of themultiplicity of carriers comprises a system that increases a likelihoodof establishing a communication channel. The carrier determining devicereduces the multiplicity of carriers to the predetermined number ofcarriers to reduce a power transmission requirement.

According to another object of the current invention, a method forestablishing a communication link is disclosed, comprising the exchangeof unmodulated carriers between an initiating communication device and aresponding communication device, to negotiate a high speed communicationlink, and the execution of a failback procedure to establish apredetermined communication link if one of the initiating communicationdevice and the responding device is unable to process the unmodulatedcarriers for negotiating the high speed communication link.

The execution of a fallback procedure comprises executing apredetermined escape procedure to establish a communication link with alegacy high speed communication device, or, alternatively, executing apredetermined explicit connection procedure to establish a communicationlink with the legacy high speed communication device.

According to a feature of the invention, the execution of the fallbackprocedure comprises executing a voiceband modulation procedure toestablish a voiceband communication link.

a still further object of the present invention pertains to a method forestablishing a communication link between a first device and a seconddevice, comprising transmitting a first capabilities list to one of thefirst device and the second device, receiving a second capabilities listtransmitted by a remaining one of the first device and the seconddevice, in response to the first capabilities list, selecting anappropriate communication mode from a plurality of communication modes,in accordance with the second capabilities list, to establish thecommunication channel, and executing a simplified initializationprocedure to re-establish the communication link in the event that oneof the first device, and the second device has entered a non-dataexchange state and data is to be exchanged between the first device andsecond device.

Another object of the instant invention pertains to a method forestablishing a communication link between a first device and a seconddevice, comprising establishing common communication capabilitiesbetween the first device and the second device, selecting an appropriatecommunication mode from a plurality of communication modes, inaccordance with the established common communication capabilities, andexecuting a simplified initialization procedure to re-establish thecommunication link in the event that one of the first device and thesecond device has entered a non-data exchange state and data is to beexchanged between the first device and second device.

Another object of the invention pertains to a method for establishing acommunication link, comprising executing a negotiation protocol in orderto establish a communication link between a first communication deviceand a second communication device, maintaining a carrier of thenegotiation protocol upon establishing the communication link, to serveas an embedded operations channel.

According to a feature of the invention, the embedded operations channeltransmits managerial data.

In another object of the instant invention, a communication device is,disclosed, comprising means for performing a handshake communicationprocedure, and means for configuring handshake communication parametersfrom a terminal using a Simple Network Management Protocol. Further, thecommunication device may also include means for monitoring the handshakecommunication parameters from the terminal. In addition, the inventionmay use an Administration, Operations, and Management (AOM) SimpleNetwork Management Protocol (SNMP) to configure and monitor a handshakeprocedure for establishing a high speed communication link.

The present disclosure relates to subject matter contained in U.S.Provisional Application Nos. 60/080,310 filed on Apr. 1, 1998;60/089,850 filed on Jun. 19, 15, 1998; 60/093,669 filed on Jul. 22,1998; and 60/094,479, filed on Jul. 29, 1998, the disclosures of whichare expressly incorporated herein by reference in their entirety.

The present disclosure also refers to the following Recommendations, thesubject matter of which is expressly incorporated herein by reference intheir entirety.

Recommendation V.8bis (09/94)—“Procedures for Starting Sessions of DataTransmission over the General Switched Telephone Network”, published byTelecommunication Standardization Sector of the ITU;

Recommendation V.8 (08/96)—“Procedures for the Identification andSelection of Common Modes of Operation Between Data Circuit-terminatingEquipments (DCEs) and Between Data Terminal Equipments (DTEs) over theGeneral Switched Telephone Network”, published by TelecommunicationStandardization Sector of the ITU;

Recommendation T.35—“Procedures for the Allocation of CCITT DefinedCodes for Non-standard Facilities”, published by TelecommunicationStandardization Sector of the ITU; and

Recommendation V.34 (10/96)—“Modem Operating at Data Signaling Rates ofup To 33,600 bit/s for Use on the General Switched Telephone Network andon Leased Point-to-point 2-wire Telephone-type Circuits”, published byTelecommunication Standardization Sector of the ITU.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features and advantages of theinvention will be apparent from the following more particulardescription of preferred embodiments, as illustrated in the accompanyingdrawings, which are presented as a non-limiting example, in whichreference characters refer to the same parts throughout the variousviews, and wherein:

FIG. 1 is a schematic block diagram of a general environment for usageof the present invention;

FIG. 2 is a schematic block diagram of the present invention under anexemplary situation in which Central Office equipment has beenprovisioned for xDSL service and Remote equipment does not employ asplitter;

FIG. 3 is a schematic block diagram of a preferred embodiment of thepresent invention used in connection with two exemplary high speed(xDSL) modems adapted to transmit signals to each other over acommunication channel;

FIG. 3′ is a schematic block diagram of the preferred embodiment of thepresent invention used in connection with a plurality of exemplary highspeed (xDSL) modems adapted to transmit signals to each other over acommunication channel;

FIG. 4 is a state transition diagram for a transaction message sequenceof an xTU-R unit;

FIG. 5 is a state transition diagram for a transaction message sequenceof an xTU-C unit;

FIG. 6 is a labeling and order format convention for octets in amessage;

FIG. 7 is a field mapping convention for data that does not reside in asingle octet;

FIG. 8 is a bit order for two octets of a Frame Check Sequence (FCS);

FIG. 9 is the structure of octets in a Frame;

FIG. 10 shows three types of fields of information;

FIG. 11 is a tree structure that links various parameters (NPars andSPars) in an Identification (I) field and a Standard Information (S)field;

FIG. 12 shows a transmission order of NPars and SPars in a message;

FIG. 13 shows the structure of octets in the Identification (I) field;

FIG. 14 shows the structure of Non-Standard information blocks in aNon-Standard information (NS) field; and

FIG. 15 shows the octet structure of data in each Non-Standardinformation block.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

According to a first embodiment of the present invention, a datacommunication system comprises a central office system 2 and a remotesystem 4, which are interfaced together via a communication channel 5,as shown in FIG. 1.

The central office system 2 includes a main distribution frame (MDF) 1that functions to interface the central office system 2 to thecommunication channel 5. The main distribution frame (MDF) 1 operates toconnect, for example, telephone lines (e.g., communication channel 5)coming from the outside, on one side, and internal lines (e.g., internalcentral office lines) on the other side.

The remote system 4 includes a network interface device (NID) 3 thatfunctions to interface the remote system 4 to the communication channel5. The network interface device (NID) 3 interfaces the customer'sequipment to the communications network (e.g., communication channel 5).

It is understood that the present invention may be applied to othercommunications devices without departing from the spirit and/or scope ofthe invention. Further, while the present invention is described withreference to a telephone communication system employing twisted pairwires, it is understood that the invention is applicable to othertransmission environments, such as, but not limited to, cablecommunication systems. (e.g., cable modems), optical communicationsystems, wireless systems, infrared communication systems, etc., withoutdeparting from the spirit and/or scope of the invention.

FIGS. 3 and 3′ illustrate detailed block diagrams of the firstembodiment of the data communication system of FIG. 1. This embodimentrepresents a typical installation, in which both the central officesystem 2 and the remote system 4 implement the instant invention. FIG.3′ differs from FIG. 3 in that FIG. 3′ illustrates the use of pluralhigh speed sections, to be discussed below.

As shown in FIG. 3, the central office system 2 comprises a low passfilter 34 and a high pass filter 38, a test negotiation block 46, a highspeed data receiving section 68, a high speed data transmitting section70, and a computer 82. Computer 82 is understood to be a genericinterface to network equipment located at the central office. Testnegotiation block 46 performs all of the negotiation and examinationprocedures which takes place prior to the initiation of an actual highspeed data communication.

The low pass filter 34 and high pass filter 38 function to filtercommunication signals transferred over the communication channel 5. Thetest negotiation block 46 tests and negotiates conditions, capacities,etc. of the central office system 2, the remote system 4, and thecommunication channel 5. The procedures of the test negotiation block 46are completed prior to, and initiate the selection of the high speedmodem receiving and transmitting sections (e.g., modems) 68 and 70. Thehigh speed receiving section 68 functions to receive high speed datatransmitted from the remote system 4, while the high speed datatransmitting section 70 transmits high speed data to the remote system4. The high speed sections 68 and 70 may comprise, but not be limitedto, for example, ADSL, HDSL, SHDSL, VDSL, CDSL modems. High speedsections 68 and 70 can be a plurality of high speed transmission deviceswhich “share” the common block 46 during the initial negotiationprocedure. The negotiation data receiving section 52 and the high speeddata receiving section 68 transmit signals to computer 82. Thenegotiation data transmitting section 54 and the high speed datatransmitting section 70 receive signals issued from the computer 82.

In the disclosed embodiment, test negotiation block 46 comprises anegotiation data receiving section 52 and a negotiation datatransmitting section 54. The negotiation data receiving section 52receives negotiation data, while the negotiation data transmittingsection 54 transmits negotiation data. The operation of the varioussections of the central office system 2 will be described, in detail,below.

Remote system 4 comprises a low pass filter 36, a high pass filter 40, atest negotiation block 48, a high speed data receiving section 72, ahigh speed data transmitting section 66, and a computer 84. Computer 84is understood to be a generic interface to network equipment located atthe remote system. Test negotiation block 48 performs all of thenegotiation and examination procedures that take place prior to theactual high speed data communication.

The low pass filter 36 and high pass filter 40 operate to filtercommunication signals transferred over the communication channel 5. Thetest negotiation block 48 tests and negotiates conditions, capacities,etc. of the central office system 2, the remote system 4, and thecommunication channel 5. The high speed receiving section 72 functionsto receive high speed data transmitted from the central office system 2,while the high speed data transmitting section 66 transmits high speeddata to the central office system 2. The negotiation data receivingsection 56 and the high speed data receiving section 72 transmit signalsto the computer 84. The negotiation data transmitting section 50 and thehigh speed data transmitting section 66 receive signals issued from thecomputer 84.

As understood from the above, FIG. 3 illustrates a construction in whichhigh speed sections 66 and 72 of the central office system 2 representsa “single box” solution, that includes one or more high speed (xDSL)modems, such as, but not limited to, the aforementioned ADSL, HDSL,SHDSL, VDSL, CDSL modems, and in which the high speed sections 68 and 70of the remote system 4 represents a “single box” solution that includesone or more high speed (xDSL) modems. On the other hand, FIG. 3′illustrates a construction in which a plurality of physically distincthigh speed sections 66 a, 66 b and 72 a, 72 b are provided, in whichhigh speed sections 66 a and 72 a of the central office system 2represent a physical first high speed (xDSL) modem, such as, forexample, an ADSL modem, and high speed sections 66 b and 72 b of thecentral office system 2 represent a physical second high speed (xDSL)modem, such as, for example, a VDSL modem, and in which the remotesystem 4 includes a plurality of physically distinct high speed sections68 a, 68 b and high speed sections 70 a, 70 b, which high speed sections68 a and 70 a of the remote system 4 represent a physical first highspeed (xDSL) modem and high speed sections 68 b and 70 b of the remotesystem 4 represent a physical second high speed (xDSL) modem. In thisregard, it is understood by those skilled in the art that one can “mixand match” the modem configuration without departing from the scopeand/or spirit of the invention. Thus, one may employ the “single box”solution with, for example, the remote system 4, and the physicallydistinct modems with, for example, the central office system 2.Alternatively, a “single box” solution (e.g., a single device thatsupports, for example, ADSL and VDSL) can be combined with a physicallydistinct modem that supports, for example, CDSL. Further, theillustration of two physical high speed modems (physically distinctmodems) in FIG. 3′ is for illustration purposes only, and thus, morethan two physically distinct modems may be used.

In the disclosed embodiment, the test negotiation block 48 comprises anegotiation data receiving section 56 and a negotiation datatransmitting section 50. The negotiation data receiving section 56receives negotiation data, while the negotiation data transmittingsection 50 transmits negotiation data. The operation of the varioussections of the remote system 4 will be described, in detail, below.

The negotiation data transmitting section 50 of the remote system 4transmits the upstream negotiation data to the negotiation datareceiving section 52 of the central system 2. The negotiating datatransmitting section 54 of the central system 2 transmits the downstreamnegotiating data to the negotiation data receiving section 56 of theremote system 4.

The central office system 2 includes a plurality of channels 6, 10, 14,16 and 18 that are used to communicate with a plurality of channels 22,26, 28, 30 and 32 of the remote system 4. In this regard, it is notedthat in the disclosed embodiment, channel 6 comprises a central voicechannel that is used to directly communicate with a corresponding remotevoice channel 32 in a conventional voice band (e.g., 0 Hz toapproximately 4 kHz), which has been filtered by low pass filters 34 and36. Further, a remote voice channel 33 is provided in the remote system4 that is not under the control of the central office system 2. Remotevoice channel 33 is connected in parallel with the communication channel5 (but prior to the low pass filter 36), and thus, provides the sameservice as the remote voice channel 32. However, since this channel isconnected prior to the low pass filter 36, the remote voice channel 33contains both the high speed data signal and a voice signal.

It is noted that the filters may be arranged to have different frequencycharacteristics, so that a communication may take place using other, lowband communication methods, such as, for example, ISDN, between voicechannels 6 and 32. The high pass filters 38 and 40 are selected toensure a frequency spectrum above 4 kHz.

Bit streams 10, 14, 16 and 18 (in the central office system 2) and bitstreams 22, 26, 28 and 30 (in the remote system 4) comprise digital bitstreams that are used to communicate between the central computer 82 andthe remote computer 84, respectively. It is understood that it is withinthe scope of the present invention that bit streams 10, 14, 16, and 18could be implemented as discrete signals (as shown), or bundled into aninterface, or cable, or multiplexed into a single stream, withoutchanging the scope and/or function of the instant invention. Forexample, bit streams 10, 14, 16 and 18 may be configured as (but are notlimited to) an interface conforming to a RS-232, parallel, FireWire(IEEE-1394), Universal Serial Bus (USB), wireless, or infrared (IrDA)standard. Likewise, it is understood that bit streams 22, 26, 28 and 30can be implemented as discrete signals (as shown in the drawings), orbundled into an interface, or cable, or multiplexed into a singlestream, as described above.

Negotiation data (e.g., control information) corresponding to thecondition of the communication line (e.g., frequency characteristics,noise characteristics, presence or absence of a splitter, etc.) isexchanged between the negotiation data receiving section 52 andnegotiation data transmitting section 54 of the central office system 2,and the negotiation data receiving section 56 and negotiation datatransmitting section 50 of the remote system 4.

The essential features of the hardware portion of the invention is thefunctionality contained in the test negotiation blocks 46 and 48, whichtest and negotiate the conditions, capabilities, etc. of the centraloffice system 2, the remote system 4, and the communication channel 5.In practice, the configuration of the central office system 2 and theremote system 4 is subject to wide variations. For example, theconfiguration of the external voice channel 33 is not under the controlof the same entities that control the central office system 2. Likewise,the capabilities and configuration of the communication channel 5 arealso subject to wide variation. In the disclosed embodiment, testnegotiation blocks 46 and 48 are embedded within modems 42 and 44.However, the functionality of test negotiation blocks 46 and 48 may,alternatively, be implemented separate and distinct from the modems 42and 44. Signals transmitted and received between the test negotiationblocks 46 and 48 are used for testing the environment itself as well ascommunicating the results of the tests between the central office system2 and the remote system 4.

The purpose of each signal path in FIG. 3 will be explained followed byan explanation of the devices used to create the signals. Examples ofspecific values for the various frequencies will be discussed in detail,below.

In the disclosed embodiment, frequency division multiplexing (FDM) isutilized for various communication paths to exchange information betweenthe central office system 2 and the remote system 4. However, it isunderstood that other techniques (such as, but not limited to, forexample, CDMA, TDMA, etc.) may be used without departing from the spiritand/or scope of the present invention.

The range from frequency 0 Hz until frequency 4 kHz is typicallyreferred to as the PSTN voice band. Newer communication methods attemptto use the frequency spectrum above 4 kHz for data communication.Typically, the first frequency where transmission power is allowedoccurs at approximately 25 kHz. However, any frequency above 4 kHz maybe used. In this regard, it is noted that tone bursts at a frequency of34.5 kHz are used to initiate T1E1 T1.413 ADSL modems. As a result, ifpossible, that frequency should be avoided in the spectrum used byprecursor negotiation methods.

The communication paths are defined in pairs, one path for an upstreamcommunication from the remote system 4 to the central office system 2,and another path for a downstream communication from the central officesystem 2 to the remote system 4. The negotiation upstream bits aretransmitted by the negotiation data transmitting section 50 of theremote system 4, and received by the negotiation data receiving section52 of the central office system 2. The negotiation downstream bits aretransmitted by the negotiation data transmitting section 54 of thecentral office system 2, and received by the negotiation data receivingsection 56 of the remote system 4. Once the negotiation and high speedtraining has been completed, the central office system 2 and the remotesystem 4 use high speed data transmitting sections 66 and 70, and highspeed data receiving sections 72 and 68 to perform a duplexcommunication.

All messages in the present invention are sent with one or more carriersusing, for example, a Differential (Binary) Phase Shift Keying (DPSK)modulation. The transmit point is rotated 180 degrees from the previouspoint if the transmit bit is a 1, and the transmit point is rotated 0degrees from the previous point if the transmit bit is a 0. Each messageis preceded by a point at an arbitrary carrier phase. The frequencies ofthe carriers, and the procedures for starting the modulation of carriersand messages, will be described below.

Once the remote system 4 begins receiving valid user downstream data,all of the various communication channels have been established and areready for the negotiation procedures to be described below.

After the remote system 4 has received the spectrum information, itanalyzes the equipment capabilities, the application desires, and thechannel limitations to make a final decision on the communication methodto use.

After the central office system 2 has received the final decision, thetransmission of the negotiation downstream data is stopped. When theremote system 4 detects the loss of energy (carrier) from the centraloffice system 2, the remote system 4 stops transmitting the negotiationupstream data. After a short delay, the negotiated communication methodbegins it's initialization procedures.

In the exemplary system of FIG. 2, the voice channel 6 is oftenconnected to a PSTN switch 300, and the functionality of the xTU-C 302is embodied in modem 42. Central office splitter 304 comprises a lowpass filter 34 and high pass filter 38. In the remote system 4, multipletelephones. 306 are connected to voice channel 32 or 33, and the xTU-R308 is implemented in modem 44.

The present invention goes to great lengths, both before the handshakeprocedure is performed and during the handshake procedure, to bespectrally polite or as non-obtrusive as possible.

In this regard, the instant invention uses a unique method (criteria)for selecting the transmission and reception carriers (frequency bands),as embodied in a PSD. The spectrum and carrier allocation for thepreferred embodiment of the present invention will now be described. Thedescription begins with a review of the upstream and downstream PSDrequirements of several different xDSL services that are co-mingled withPOTS or ISDN services. Implications of the xDSL PSDs on the presentinvention PSD are also discussed.

Downstream carriers are transmitted by the negotiation data transmittingsection 54 of the central office system 2, and upstream carriers aretransmitted by the negotiation data transmitting section 50 of theremote system 4.

The present invention is used to initiate or activate many types ofexisting and future xDSL services. The requirements of the various xDSLservices have been taken into consideration in the design of presentinvention. This description addresses two inter-related considerations:spectrum and activation methods. In the present invention, suitablebands were selected for the transmission of the negotiation datachannels. The bands were selected based upon several criteria, includingconsidering the existing overall PSDs of the xDSL services and also theactivation signals of existing xDSL services.

Examples of various spectra of typical xDSL and existing services thatmight be negotiated by the present invention are shown in Table 1. Forpurposes of definition, “upstream” and “downstream” directions using thenomenclature from the various xDSL services are indicated in Table 2.Table 3 lists the initiating activating sequences of several xDSL.Together these tables outline the typical environment in which thepresent invention must be capable of operating.

TABLE 1 survey of existing relevant spectra Total Upstream Down StreamBandwidth Bandwidth Bandwidth Modulation Lower Upper Lower Upper LowerUpper (Document) (kHz) (kHz) (kHz) (kHz) (kHz) (kHz) ITU-T G.992.1 261,104 26 138 26 1,104 Annex a ITU-T G.992.2 26 1,104 26 138 26 1,104Annex a (FDM) ITU-T G.992.1 138 1,104 Annex B ITU-T G.992.1 26 50 26 5026 50 Annex C ITU-T G.992.2 26 50 26 50 26 50 Annex C T1E1 HDSL2 0 400 0900 or ITU-T G.shdsl VDSL (with 300 30,000 300 30,000 300 30,000European ISDN) DTS/TM- 06003-1(draft) V0.0.7 (1998-2) Section 8.2Frequency plan

TABLE 2 DEFINITIONS OF UPSTREAM AND DOWNSTREAM Modulation (Document)Upstream Downstream G.992.1 xTU-R to xTU-C xTU-C to xTU-R T1.413 Cat 1w/Analog filters ATU-R to ATU-C ATU-C to ATU-R G.992.2 xTU-R to xTU-CxTU-C to xTU-R DMT with only 64 tones xTU-R to xTU-C xTU-C to xTU-RG.hdsl NTU to LTU LTU to NTU HDSL2 NTU to LTU LTU to NTU VDSL (withEuropean ISDN) NT to ONU (LT) ONU (LT) to NT-R DTS/TM-06003-1(draft)V0.0.7 (1998.2) Notes xTU-R, NTU, NT indicate customer side xTU-C, LTU,ONU indicate network side

TABLE 3 Activation signals of existing xDSLs Modulation (ITU DocumentRef. No.) Initiator Responder Comment G.992.1 None - will use handshakeprocedure G.992.2 None - will use handshake procedure T1.413 Issue 1R-ACT-REQ C-ACT1 34.5 kHz sinusoid with 207 kHz cadence of: (#48) 128symbols on C-ACT2 64 symbol @ −2 dBm 190 kHz (˜16 ms) (#44) 64 symbol @−22 C-ACT3 dBm (˜16 ms) 896 symbols off 224 kHz (˜221 ms) (#52) C-ACT4259 kHz (#60) T1.413 Issue 2 (same as Issue 1) (same as issue 1) ETSI:ADSL over same as T1.413 but C-ACT2m ISDN k = 42; 181.125 kHz 319 kHz(#74) C-ACT2e 328 kHz (#76) RADSL CAP RTU-R transmits Using 282 RSO +trailer kHz and (pseudo noise at 306 kHz symbol rate) Using 68 kHz and85 kHz G.hdsl (2B1Q) LTU transmits S0 NTU trans- mits S0 G.hdsl (CAP -LTU transmits CS0 NTU trans- Annex B) 3150 symbols of mits RS0; pseudonoise at 3150 symbols symbol rate of pseudo noise at symbol rate HDSL2TBD VDSL Not defined DTS/TM-06003-1 yet (draft)

With respect to the bands used by ADSL modems, the present inventionuses the following detailed criteria to select appropriate carriers forthe upstream negotiation channel and the downstream negotiation channel:

-   1. Consider all of the services/families known today (e.g.,    G.992.1/G.992.2 Annex a, Annex B, Annex C, HDSL2);-   2. Upstream and downstream negotiations will not use the same    frequencies (i.e.; the preferred embodiment does not use echo    canceling);-   3. FDM filter implementations (with a few non-essential    additions)—e.g., avoid upstream/downstream interleaving;-   4. Avoid existing T1.413 activation tones (e.g., tone numbers 8, 44,    48, 52, 60);-   5. G.992.1 Annex a and G.992.2 Annex a use the same upstream and    downstream carriers. G.992.1 Annex C and G.992.2 Annex C use the    same upstream and downstream carriers;-   6. At least one carrier associated with G.992.1 Annex a is the same    as the carrier used with G.992.1 Annex C. At least one carrier of    G.992.2 Annex a is the same as the carrier used with G.992.2    Annex C. (For both upstream and downstream);-   7. The ADSL Annex a downstream band is reduced to tones 37 through    68, based on G.992.2;-   8. Be reasonably robust against Intermodulation products;-   9. a grid for decimation (mainly applicable for Annex a and Annex    B). This allow a sample clock that is lower than the Nyquist rate to    still extract the required information, because the folded over    signals in the spectrum fall directly on top of each other. Since    the tones for Annex C have special requirements, they often cannot    be aligned on the same grid as the Annex a and Annex B tones;-   10. Higher frequency tones should be spaced farther apart to reduce    leakage in the filters;-   11. In general, there are 3 tones per Annex (however, Annex C has 2    primary tones each way, and a third borderline tone);-   12. Tones between 14 and 64 should not be transmitted in a TCM-ISDN    environment; and-   13. Avoid (if possible) RADSL activation frequencies. Thus, in the    upstream carrier, avoid 68 kHz (˜#16) and 85 kHz (˜#20). In the    downstream carrier, avoid 282 kHz (˜#65) and 306 kHz (˜#71).    Based on the above discussion, a preferred Embodiment #1 uses the    following carriers:

Family/Direction Tone Index Comment 4.3 k Upstream 9, 11, 13, 21, 33,37, 41 (Annex a and B tones use the grid 4N + 1) 4.3 k Downstream 6, 7,(26), 50, 58, 66, 74, (Annex a and B tones use 90, 114 the grid 8N + 2)4 k fanily Reserve Tone area 2-5A preferred Embodiment #2 uses the following carriers:

Family/Direction Tone Index Comment 4.3 k Upstream 9, 11, 15, 23, 35, 39(Annex a and B tones use the grid 4N − 1) 4.3 k Downstream 6, 7, (26)50, 58, 66, 74, (Annex a and B tones use 90, 114 the grid 8N + 2) 4 kfamily Reserve Tone area 2-5A preferred Embodiment #3 uses the following carriers:

Family/Direction Tone Index Comment 4.3 k Upstream 9, 12, 21, 27, 33,36, 39 (All tones use the grid 3N) 4.3 k Downstream 6, 7, (26), 50, 58,66, 74, (Annex a and B tones use 90, 114 the grid 8N + 2) 4 k familyReserve Tone area 2-5A preferred Embodiment #4 uses the following carriers:

Family/Direction Tone Index Comment 4.3 k Upstream 7, 9, 17, 25, 37, 45,53 (Annex a and B tones use the grid 4N + 1) 4.3 k Downstream 12, 14,40, 56, 64, 72, (Annex a and B tones use 88, 96 the grid 8N) 4 kUpstream 3 4 k Downstream 5

TABLE 4 CARRIER PREFERRED EMBODIMENT #1

Comments on the selected carriers:

-   1. The upstream and downstream carriers are completely separated;-   2. The upstream and downstream bands of the existing T1.413    activation tones are preserved;-   3. Annex B allows the optional use of tones below number 33, in    which the ATU-x may be able to use some but not all of the carriers    originally designated for Annex a;-   4. Annex B upstream band and Annex a downstream band essentially    overlap, so the common band was divided between the two    requirements;-   5. The tones associated with Annex a and B are set along a common    grid;-   6. * Tone 26 may optionally be used for downstream transmission, so    that a much lower frequency could be used in situations in which    high frequency line attenuation exists. However, since it is in the    midst of the upstream band, certain filter implementations may    preclude it's usage;-   7. Tone 4 falls in the null of TCM-ISDN spectrum, so there is some    positive SNR there and it is in common with Annex B;-   8. Tone 4 was selected as the frequency for Annex B's C-ACT2m; and-   9. The band to allocate Annex B upstream tones is very narrow. Using    3 carriers places the two outer carriers very near the band edge. If    2 carriers are sufficient, they could have much better placement. In    that case, the appropriate upstream grid is 4N−1 and all of the    revised upstream carrier values are shown in Table 5.

TABLE 5 UPSTREAM CARRIER PREFERRED EMBODIMENT #2 Down UpstreamDownstream UP Avoids 8 16 20 HDSL2 Anx. a 11 15 23 Anx. B 35 39 Anx. C 911 Index 6 7 8 9 11 15 16 20 23 26 31 35 39 44 48 50 52 58 60 63 66 6874 90 114 255

TABLE 6 UPSTREAM CARRIER PREFERRED EMBODIMENT #3 Down UpstreamDownstream UP Avoids 8 16 20 HDSL2 Anx. a 9 12 21 27 Anx. B 33 36 39Anx. C 9 12 Index 6 7 8 9 12 15 16 20 21 27 33 36 39 44 48 50 52 58 6063 66 68 74 90 114 255

TABLE 7 CARRIER PREFERRED EMBODIMENT #4

Although Tables 4-7 describe preferred embodiments, it is understoodthat other sets of frequencies can be used for other environments, whilestill conforming to the selection criteria described in this invention.

The frequencies of the carriers are derived by multiplying a base familyfrequency (e.g., 4.3125 kHz, or 4.000 kHz) by the carrier index. Toachieve robustness, multiple carrier symbols are used for each data bit.The 4.0 kHz family, designated as family B, achieves a bit rate of 800bits/s by dividing the 4000 symbols/sec rate by 5. The 4.3125 kHzfamily, designated as family a, achieves a bit rate of 539.0625 bits/sby dividing the 4312.5 symbols/sec rate by 8.

In the above carrier selection embodiments for the ADSL bands, severalxDSL requirements were simultaneously examined. It is also prudent to beaware of the spectrum used by VDSL modems. However, as of the time ofthis invention, VDSL transmission techniques have not been finalized.Thus, it is advisable to consider the following criteria andconsiderations when selecting carriers for use with VDSL devices(modems):

-   1. Some VDSL splitter designs begin the HPF roll-off at    approximately 600 kHz. As a result, some carriers should be above    600 kHz(e.g., ADSL tone #140). Other splitter designs roll-off at    approximately 300 kHz(e.g., ADSL tone #70). Thus, carriers above    those frequencies would be needed;-   2. Although there is discussion of an ADSL-compatible mode of VDSL    which ensures no interference to ADSL lines, by significantly    reducing power in the carriers below 1.1 MHZ, a VDSL device can    transmit carriers in compliance with the ADSL PSDs. Thus, care    should be taken not to introduce performance degradation to existing    services, and in particular, ADSL service;-   3. In this regard, current VDSL proposals call for carriers to be    spaced at 21.625 kHz and 43.125 kHz. However, it is likely that    devices will initiate in the 43.125 kHz mode, so carriers with a    grid of 43.125 kHz is preferred;-   4. Carriers should be below 3 MHZ (equivalent to ADSL tone #695), so    that they can be detected on the longest of VDSL capable lines;-   5. Carriers should avoid known HAM radio bands, such as, for    example, 1.8-2.0 MHZ (which is equivalent ADSL tones #417-#464) in    North America, or 1.81-2.0 MHZ in Europe;-   6. Carriers should be selected so as to avoid interference from AM    radio stations;-   7. VDSL may employ Time Division Duplex (TDD) techniques.    Accordingly, upstream and downstream separations need not be so    strict;-   8. Signals above 1.1 MHZ in the VDSL band should be transmitted in    synchronism with the ONU's chosen superframe structure, in order to    avoid Near End Crosstalk (NEXT) into the other TDD VDSL lines in the    binder; and-   9. At least one set of carriers should be inside the VDSL spectrum    plan.

Based on the above, preferred carriers for VDSL, according to thepresent invention, are as follows:

Downstream Grid=(ADSL downstream grid)×(VDSL grid)=(8N+2)×(10)→100, 180,260, 340, etc.

Upstream Grid=(ADSL upstream grid)×(VDSL grid)=(4N−1)×(10) →350, 390,470, 510, 550, etc.

The implicit channel probing feature of the present invention can beused to assess the characteristics of the communication channel whileconcurrently transmitting information over the communication channel.

Channel probing is performed implicitly by observing all of theinitializing carriers sent during the activation sequence, and to verifywhich carriers were sent, by reading the corresponding bits indicated inTables 23 and 24. During the reception of unmodulated carriers, thexTU-C, using the negotiation data receiving section 52, and the xTU-R,using the negotiation data receiving section 56, monitor thecommunication channel (line) to perform a spectrum analysis of thesignal to calculate spectrum information. The accuracy of the implicitchannel probing need not be precise; it is only necessary to obtain arough estimate of the SNR in the channel. An xTU-X alters (changes) it'smodulation and parameters selections based on the contents of a CL/CLRmessage exchange and the SNR from the implicit channel probe.

Another problem addressed by the current invention relates to the use oftoo many carriers, or the use of too much transmission power, during aninitialization procedure. In some environments, it is necessary toreduce the number of carriers used to transmit negotiation informationin order to be spectrally polite. In such cases, it is difficult todetermine which tones the receiver is actually receiving.

According to a first example of the instant invention for reducing thenumber of carriers, referred to as a Pair Phase Reversal example,upstream and downstream tones are paired. When an xTU-x receives a tonefrom a particular pair, it transmits phase reversals on it'scorresponding mate (pair) before beginning a modulated carrier.

However, this example exhibits the following limitations:

-   1. One tone of the pair mate might not be usable because of bridge    taps or interference; thus, the other pair mate would be idle; and-   2. The carriers cannot always be uniquely paired.

a second example of is referred to as a Modulate Carrier Before Messagesexample. After sending an unmodulated carrier and before sending amodulated carrier, messages begin with flags, the xTU-X modulates all ofit's carriers to indicate which carriers it is receiving. Codes can becreated by transmitting concatenated 50% duty cycle patterns of 1's and0's, with different lengths indicating different carriers. The fixedduty cycle allows reception without octet synchronization.

However, this example exhibits the following limitations:

-   1. The scheme is not bit or time efficient;-   2. It would be preferable to octet-synchronize first and then send    the information in a digital message;-   3. This scheme increases the time required for the activation    sequence; and-   4. This coding scheme does not include error correction.

a third example is referred to as a Carriers Used and Request Transmitscheme. Based upon the limitations of this scheme (discussed below),example three is the preferred scheme. Carriers to be used in asubsequent session are negotiated via octets in message transactions.

During an initial state, every applicable carrier transmits CL/CLRmessages. a list of transmitted carriers is indicated in Table 23 andTable 24. Parameters in the CL/CLR messages used to determine(negotiate) which carriers to use for subsequent messages are shown inTable 34 and Table 35. The number of transmitted carriers may be reducedin the same transaction, such as, but not limited to, MR, MS, ACK, NAKmessages in the same transaction. The number of transmitted carriers mayalso be reduced in subsequent sessions and transactions that initializewith MS or MR messages. As with MS for MS message contents and states,the xTU-X uses some memory to save the usable carrier information.

If a channel impediment, such, as but not limited to, an interferer or abridge tap arises later, an initialization timeout from the initiatingxTU-X allows all of the possible tones to be used from the initiatingxTU-X.

In their initial states, the xTU-R and xTU-C are encouraged to transmitas many carriers as possible, in order to determine whether any commoncarriers exist. a pair of xTU-R and xTU-C negotiate using predeterminedprocedures, defined above, to specify the transmission of a reducednumber of carriers for subsequent messages and subsequentinitializations.

If an xTU-X has been instructed to reduce the number of carriers in themidst of completing a transaction, the xTU-X only reduces the carrierswhen it is in the process of transmitting flags. After the transmissionof a complete flag, the xTU-X transmits an unmodulated carrier on theredundant carriers for a period of two octet times before stoppingtransmission on the redundant carriers.

If an xTU-R and xTU-C have negotiated to use a reduced set ofinitialization carriers by the procedures defined above, the reduced setof carriers shall be used for a subsequent initialization. If ananticipated response is not received within time T₁, prior instructionsfrom the other xTU-X to reduce the number of carriers are ignored andthe initialization scheme re-commences.

Either the central office (xTU-C) system 2 or the remote (xTU-R) system4 may initiate modulation channels. The negotiation data transmittingsection 50 of the remote system 4 transmits the upstream negotiationdata to the negotiation data receiving section 52 of the central system2. The negotiating data transmitting section 54 of the central system 2transmits the downstream negotiating data to the negotiation datareceiving section 56 of the remote system 4. After the negotiationmodulation channels have been established, the remote station is alwaysconsidered the initiating modem in terms of the transaction messages.Likewise, the central office terminal is thereafter referred to as theresponding station.

a discussion of the initiation by the xTU-R will now be described,followed by a discussion of the initiation by the xTU-C.

The initiating xTU-R transmits unmodulated carriers selected from eitherone or both families of the Upstream group, via negotiation datatransmitting section 50. When the negotiation data receiving section 52receives the carriers from the xTU-R for a predetermined period of time(at least 200 ms in the preferred embodiment), the responding xTU-Ctransmits unmodulated carriers, via negotiating data transmittingsection 54, selected from only one family of the Downstream group. Afterreceiving the carriers using negotiation data receiving section 56 fromthe xTU-C for the predetermined period of time (e.g., at least 200 ms),the xTU-R DPSK modulates, using negotiation data transmitting section50, only one of the family of carriers and transmits a predeterminedflag (e.g., 7E₁₆) as data. If the xTU-R initiated with carriers selectedfrom both families, the xTU-R stops transmitting carriers from the otherfamily before it begins modulating carriers from the selected family.After receiving the flag, via negotiation data receiving section 52 fromthe xTU-R, the xTU-C DPSK modulates only one of the family of carriers(using negotiating data transmitting section 54) and transmits flag(e.g., 7E₁₆) as data.

To facilitate the finding of a common set of carriers (if they exist),if an xTU-C receives carriers of a family that it cannot transmit, itnevertheless responds by transmitting carriers from a family it iscapable of transmitting. This allows the xTU-R to detect the presence ofthe xTU-C, and, if it has the capability to do so, attempt an initiatingprocedure with a different carrier family.

In the disclosed embodiment, the xTU-C and the xTU-R monitor the linefor existing services prior to transmitting carriers, to avoidinterfering with existing services, using the negotiation data receivingsections 52 and 56, respectively.

The xTU-C transmits identical data, with identical timing on any and alldownstream carriers. The xTU-R transmits identical data with identicaltiming on any and all upstream carriers.

The initiating xTU-C transmits unmodulated carriers selected from eitherone or both families of the Downstream group using the negotiation datatransmitting section 54. After receiving the carriers, using negotiationdata receiving section 56, from the xTU-C for (in the preferredembodiment) at least 200 ms, the responding xTU-R transmits unmodulatedcarriers using the negotiation data transmitting section 50, selectedfrom only one family of the Upstream group. After the carriers arereceived for at least 200 ms by the negotiation data receiving section52 of the xTU-R, the xTU-C begins DPSK modulating only one of the familyof carriers using the negotiating data transmitting section 54, andtransmits ones (FF₁₆) as data. If the xTU-C is initiated with carriersselected from both families, the xTU-C stops transmitting carriers fromthe other family before it begins modulating carriers from the selectedfamily. After receiving ones from the xTU-C, the xTU-R DPSK modulatesonly one of the family of carriers and transmits flags (7E₁₆) as data.After the flags are received from the xTU-R, the xTU-C DPSK modulatesonly one of the family of carriers and transmits flags (7E₁₆) as data.

In order to facilitate the finding a common set of carriers (if theyexist), if the xTU-R receives carriers of a family that it cannottransmit, it nevertheless responds by transmitting carriers from afamily it is capable of transmitting. This allows the xTU-C to detectthe presence of the xTU-R and attempt an initiation with a differentcarrier family, if it has the capability to do so.

According to the instant invention, the xTU-C and the xTU-R monitor thecommunication line (using the negotiation data receiving sections 52 and56, respectively), for existing services prior to transmitting carriers,in order to avoid interfering with existing services.

The xTU-C transmits identical data with identical timing on any and alldownstream carriers. The xTU-R transmits identical data with identicaltiming on any and all upstream carriers.

In the present invention, an error recovery mechanism comprises (but isnot limited to) the transmission of an unmodulated carrier of ones(FF₁₆), or flags (7E₁₆) that shall not exceed, for example, a timeperiod of 1 second. An xTU-x may restart the initiation procedure or mayoptionally start alternative initiation procedures.

If only one communication device in the communication link implementsthe present invention's preferred activation method, a high speedcommunication may not be possible. The following describes mechanisms tofallback (or escape) to legacy communication systems, such as, but nolimited to, legacy DSL systems or voiceband communication systems.Fallback to xDSL systems will be described first followed by adescription of the voiceband fallback procedures:

1. Fallback Methods to Legacy xDSL Modulations

Some legacy xDSL systems (examples of which are shown in Table 3) do notimplement the present invention. The present invention includesprocedures to fallback to a legacy xDSL activation method. The presentinvention is intended to be a robust mechanism for activating amultiplicity of xDSL modulations in the presence of unknown equipmentwith unknown transceiver PSDs. The activation of regional standards(i.e., legacy devices) can be handled by two different methods: animplicit method (e.g., activation via escape), or an explicit method(e.g., activation via nonstandard facilities or standard information).Both methods are used to cover the multitude of initialization methods.

The activation via escape method facilitates the startup of devicesprior to the present invention beginning the negotiation modulation.This allows the startup of devices which, for example, implement Annexa, B, or C of a predetermined communication standard (with differingPSDs) and a legacy xDSL system, such as, but not limited to T1.413. Thepresent invention monitors several different frequency bands usingxTU-C's data receiving section 52 or xTU-R's data receiving section 56.Thus, a device that also supports a regional standard (such as, forexample, T1.413) can concurrently (or nearly concurrently) monitor forthe regional standard activation signals while monitoring for theactivation signals of the present invention. a procedure forinterworking with the ANSI T1.413 protocol is shown in Table 8.

TABLE 8 ESCAPE ACTIVATION WITH T1.413 DEVICES Device: CapabilitiesAlgorithm ATU-C T1.413 Waits for R-ACT-REQ, Ignores present inventionactivation signals Initiates T1.413 when receives R-ACT-REQ ATU-C T1.413& Waits for R-ACT-REQ or present invention present invention initiatingtone(s) Initiates as appropriate ATU-R T1.413 Transmits R-ACT-REQ andwaits for C-TONE or C-ACT Ignores any present invention activationsignals from the ATU-C ATU-R T1.413 & Transmits present inventionactivation present invention signals. If no response to presentinvention activation signals, transmits R-ACT-REQ

The activation via non-standard facilities or standard informationembodiment allows the interworking of devices after the initializationof the handshake modulation, by indicating the legacy communicationsystem in a message. The message may use either a non-standardinformation (NS) field or a Standard Information (S) field.

The present invention allows the transmission and reception of anon-standard message that indicates a different modulation. Regionalstandards can be explicitly negotiated through non-standard facilities.

The present invention also provides for the transmission and receptionof a standard information message that indicate a different modulation.Regional standards can be explicitly negotiated through a code point inthe standard information field.

It is understood that other DSL communication systems, such as, but notlimited to, for example, RADSL, can be negotiated using the sameexplicit and implicit methods discussed above for T1.413, withoutdeparting from the spirit and/or scope of this invention.

2. Fallback Methods to Voiceband Modulations

Fallback methods for voiceband modulations are similar to the fallbackmethods described above for xDSL modulations; that is, both explicit andimplicit methods exist.

The initial signals for a voiceband modulation are specified in ITU-TRecommendation V.8 and ITU-T Recommendation V.8bis. In the explicitmethod, after the V.8 or V.8bis code points are selected in an MSmessage, acknowledged with an ACK(l) message, and the present inventionhas executed (been completed), the V.8 or V.8bis procedures begins. ThexTU-R takes on the roll of a V.8 calling station and the xTU-C takes onthe roll of a V.8 answering station.

In the implicit method, if an xTU-X initiates a handshake session bytransmitting negotiating tones but does not receive a response from apossible xTU-X at the other end of the communication channel 5, theinitiating xTU-X may assume that the other xTU-X does not support a highspeed communication, and may then switch to initiating a communicationusing voiceband procedures such as V.8 and V.8bis.

The instant invention also addresses the prior art problem of havinglong or complicated initialization transactions when eithercommunication device in the communication link needs to transmit data.

In general, the xTU-C is usually always ON, or will have been turned ONbefore the xTU-R is turned ON. The xTU-R can always remain ON, but it ismore likely that there will be periods in which the xTU-R is turned OFFor placed into a “sleep” mode (a mode in which the xTU-R is placed in astandby mode to minimize electrical power consumption). If the xTU-R isin the sleep mode, the central side needs to “wake up” the xTU-R beforea data transmission can occur. Four basic transactions for accomplishingthis are described in Table 9.

TABLE 9 Four Basic Transaction Needs Name Description CharacteristicsRemote First very first time initialization ATU-R initiates modulationTime of a dedicated circuit full capabilities exchange typicalinitialization by a mobile unit Remote reestablish a previously nego-ATU-R initiates modulation Reestablish tiated operating modereconfirmation of previous mode through minimal exchange Central PushThe network side wishes the ATU-C initiates modulation (First Time)ATU-R to activate in order full capabilities exchange for the network todeliver a “push” service. Central Push Push application desires to ATU-Cinitiates modulation Reestablish reestablish. typically occurs after aprevious full capabitities exchange minimal exchange

Since the xTU-R will always send the first message of a transaction, andthe first message should be as meaningful as possible when the xTU-Rinitializes the modulation, the present invention uses a preferredinitialization protocol scheme shown in Table 10. Alternatively, aninitialization protocol scheme illustrated in Table 11 may be used.However, it is understood that variations to these transactions may bemade without departing from the spirit and/or scope of the instantinvention.

TABLE 10 Transactions Preferred Scheme #1 Transaction sequence xTU-RxTU-R # Name → xTU-C → xTU-R → xTU-C → → Z First Time CLR CL MS ACK/ NAKY Reestablish MS ACK/ NAK W Central Push RC CLR CL MS ACK/ First TimeNAK X Central Push RC MS ACK/ Reestablish NAK Where: CL Transmit aCapabilities List This message conveys a list of possible modes ofoperation of the transmitting station. CLR Transmit a Capabilities Listand Request the other unit to also transmit a capabilities list Thismessage conveys a list of possible modes of operation of thetransmitting station and also requests the transmission of acapabilities list by the remote station. MS Mode Select - specify theintended mode. This message requests the initiation of a particular modeof operation in the remote station. ACK Acknowledge the selected mode.ACK(1): This message acknowledges receipt of an MS message andterminates a transaction. It may also be used to acknowledge receipt ofpart of a CL-MS message combination and request transmission of theremainder of the message combination. ACK(2): This message acknowledgesreceipt of a CL, CLR or MS message and requests the transmission ofadditional information by the remote station, providing the remotestation has indicated that additional information is available. NAK NotAcknowledge the selected mode This message indicates that the rcceivingstation is unable to interpret a received message or to invoke the moderequested by the transmitting station. Four NAK messages are defined:NAK(1) (a.k.a. NAK-EF) indicates that the receiving station is unable tointerpret the received message because it is an Errored Frame;NAK(2)(a.k.a. NAK-NR) indicates that the receiving station istemporarily unable to invoke the mode requested by the transmittingstation; NAK(3)(a.k.a. NAK-NS) Indicates that the receiving stationeither does not support or has disabled the mode requested by thetransmitting station; and NAK(4) (a.k.a. NAK-NU) indicates that thereceiving station is unable to interpret a received message. RC (a.k.aREQ) Revert control of the transaction to the xTU-C The message tellsthe xTU-C to take control. MR This message requests the transmission ofa mode select message by the remote station.

Although there are names and scenarios associated with the transaction,the names should merely be considered as informational in nature.

All messages in a transaction are required.

The RC message contains only one bit of information. Setting the bit to“1” represents that the xTU-C was “surprised” by the push request, or isin a state of confusion. In this situation, it is recommended (but notmandated) that the xTU-C use transaction X instead of W.

MS always includes the desired mode.

If a xTU-R NAKs in a transaction X but wishes to keep trying, it shallsend NAK(_) and then transaction Z.

On the other hand, if an xTU-C NAKs, the xTU-R should send RC to starttransaction X or W.

The following is noted in the situations where the xTU-C has initiatedthe modulation:

-   1. If the xTU-R is prepared for the xTU-C to dominate, transaction X    or W should be utilized. This should be the typical case when the    ATU-C initiates the modulation;-   2. However, if the xTU-R is to have equal control, it should use    transaction Z;-   3. Although transaction Y could be used, it is overly presumptuous    on the part of the xTU-R; and-   4. The initiation of modulation by the xTU-C can also be used in    conjunction with a power management system.

TABLE 11 Transactions Preferred Scheme #2 Transaction number xTU-R xTU-CxTU-R a (same as Y) MS→ ACK/NAK B (same as X) MR→ MS→ ACK/NAK C(modification of Z and W) CLR→ CL→ ACK/NAK

All permitted transactions will now be described.

Transactions involving the use of messages CL and CLR permit a transferor exchange of capabilities between the two stations. Transactionsinvolving the use of message MS allow a specific mode to be requested byeither station and permit the other station to accept or decline thetransition to the requested mode. Transaction a or B are used to selectan operating mode without first establishing their common capabilities.Transaction C is used to exchange information about each station'scapabilities. Transaction B is intended to allow the responding stationto take control of the outcome of the transaction.

FIGS. 4 and 5 illustrate state transition diagrams for a secondtransaction embodiment. The state transition diagrams show stateinformation (e.g., the state name and current transmitted message) andtransition information (e.g., the received message that caused the statechange). In FIGS. 4 and 5, message names followed by an asterisk (*)indicate that the state transition may be taken upon the reception of acomplete message, or upon the reception of one or more segments of themessage.

When a message is received with the “additional information available”parameter set to binary ONE in the identification field, the receivingstation may send an ACK(2) message to request that further informationbe sent. When the ACK(2) message is received, further information issent. The transmission of signals associated with a selected mode beginsimmediately after the transmission of ACK(1).

When a station receives an MS message requesting a mode that it isunable to invoke, the station responds by sending a NAK. If an invalidframe is received in any state, the receiving station sends a NAK(1) andimmediately returns to an Initial State. If an xTU-X has transmitted amessage, but is not receiving, flags or valid message data from theother xTU-X the error recovery procedures (described above) apply. If anxTU-X has transmitted a message and is receiving flags, it waits for apredetermined period of time, for example, 1 second, beforere-transmitting the sane message. If the xTU-X has transmitted the samemessage a certain number of times (e.g., 3 times) without receiving avalid message response from the other xTU-x, the transmitting xTU-Xtransmits a Hangup message and stops transmitting the carrier. Ifdesired, the xTU-x may restart the initiation attempt or startalternative initiation procedures.

The maximum number of octets in any Information Field is 64. If theinformation exceeds this limit, the remainder of the information may becontained in subsequent messages. To indicate that further informationexists, an “Additional Information Available” parameter is set to binaryONE in the identification field of the transmitted message. Thisinformation, however, shall only be sent if, on receiving the message,the remote station sends an ACK(2) message requesting furtherinformation.

Where non-standard information is present in the information field, thestandard and non-standard information may be conveyed in separatemessages. If the information to be conveyed in the CL message cannot beconveyed in a single message, and the “Additional Information Available”parameter is set to binary ONE, a response is required from thereceiving station in order for the transmitting station to completetransmission of the combined CL-MS messages, irrespective of whether theadditional information is to be sent. In this case, an ACK(1) shall besent if no further information is required.

The current invention also addresses the desirability of transmittinginformation in additional to the equipment capabilities. (e.g, channelinformation, service parameters, regulatory information, etc.) duringthe negotiation procedure. In this regard, the present inventioncontains several different and additional types of information, ascompared to V.8bis and V.8. The types of information emphasize servicein requirements instead of “application groups”. It is noted that thetypes of information are merely examples of the types and methodology ofparameter exchange, and thus, modifications (variations) may be madewithout departing from the spirit and/or scope of the invention.

The preferred embodiment of the present invention has the generalorganizational structure shown in Table 12. Modulation independentinformation is presented in an “Identification” field, and modulationdependent information is presented in a “Standard Information” field. Ingeneral, service parameters and channel capabilities information areindependent of the various xDSL modulations. The overall composition ofmessages according to a first example is shown in Table 13, while Table14 illustrates a second example.

TABLE 12 Information Organization Structure Identification (ServiceParameters/Channel Capabilities) NPar(1) (No sub- parameters)Identification (Service Parameters/Channel Capabilities) SPar(1) (sub-parameters) Message Type and version Vendor Identification using T.35codes Amount/type of bandwidth number of data channels desired knownsplitter information spectrum usable frequencies - generalization of FDMand overlapped spectrum carrier families, groups, and tone numbers beingtnansmitted Standard Information (Modulations/protocols) NPar(1)Standard Information (Modulations/protocols) SPar(1) Which type of xDSLetc. Regional considerations (i.e., use of a specific Annex in aRecommenda- tion) Protocol information error correction, datacompression etc. Non-standard Information

TABLE 13 Overall Message Composition (Embodiment #1) IdentificationCountry Standard Code Informa- Provider tion Length Service Modula- NonMessage Provider & tions & Standard Type & Code Channel ProtocolsInformation Version (1 + 1 + parameters available (3 + M + Messages (1octet) L octets) (? octets) (? octets) L octets) RC Y Y — — — CLR Y Y YY as necessary CL Y Y Y Y as necessary MS Y Y Y Y as necessary ACK Y Y —— — NACK Y Y * * — Notes: * NACK includes the reason for the NACK bysetting the bits of the offending parameters

TABLE 14 Overall Message Composition (Embodiment #2) Standard NonStandard Identification Information Information Message Type & RevisionVendor ID Service & Channel Modulations &$\quad{1 + {\sum\limits_{i = 1}^{N}\left( {7 + M_{i}} \right)}}$Messages (2 octets) (8 octets) parameters Protocols available octets MRX — — — — CLR X X X X as necessary CL X X X X as necessary MS X — X X asnecessary ACK X — — — — NAK X — — — — REQ X — — — —

The following describes the organizational details within each category.

Parameters specific to a given xDSL modulation should always appearunder the appropriate modulations category. Of those modulationparameters, some of them might be more general than others, and can havehigher positions in the NPars/SPars tree.

Parameters that are negotiated in T1.413 are also negotiated in thepresent invention (with the exception of Vendor ID, which uses T.35codes). However, there are a few cases when related parameters need tobe negotiated by the present invention:

-   -   If the optionality of the parameters in G.992.1 differ from        T1.413;    -   If the parameter actually needs to be negotiated instead of just        indicated; or    -   If a general preference about a class of parameters needs to be        indicated.

If the parameter is very general, it should be negotiated in the ServiceParameters octets on the Identification field. If the parameter isfairly closely related to the modulation, it should be negotiated in the2^(nd) level of the modulation's standard information octets. Even ifthese modulation parameters are fairly similar among variousmodulations, they are coded separately for each modulation. Also, otherxDSL modulations, such as, for example, VDSL, have some very differentparameters, making it very difficult to have one large list ofparameters trying to satisfy all of the xDSL requirements andcapabilities. As a result, there is some redundancy in the modulationparameters, in much the same way that redundancy exists with V.8bis.Further, many of the parameters under the various applications areidentical.

Three types of parameters/options exist; manufacturing, provisioning andnegotiated options.

1. Manufacturing Options

Manufacturing options are defined as optional portions of aspecification that a manufacturer includes/chooses in the productdesign. An example of a manufacturing option is to employ EC vs. FDM.Manufacturing options must be disclosed and acknowledged in the startup,since a communication would be impossible without commonality betweenthe various devices.

2. Provisioning Options

Provisioning options are defined as optional capabilities that are insome way fixed a priori. An example of a provisioning option is the Looptiming at the CO that is required to be mastered by either the CO or theCP. The CO capability is normally fixed by a priori decision prior tothe negotiation. It is noted that this option can be merged into eitherthe manufacturing or negotiated options. As a result, only a few optionsare in this category.

3. Negotiated Options

Negotiated options are defined as an option in which an item must beselected from a list of (mandatory available) options. An example of anegotiated option is the data transmission rate. In negotiated options,the transmission rate is made peer to peer.

The information coding format for the present invention will now bedescribed with respect to Tables 15-45. The discussion provided withrespect to Tables 15-18 are provided as background information. Tables20-45 are directed to the features of the instant invention.

The basic format convention used for messages is illustrated in FIG. 6.Bits are grouped into octets. The bits of each octet are shownhorizontally and are numbered from 1 to 8. Octets are displayedvertically, and are numbered from 1 to N. The octets are transmitted inascending numerical order. Within an octet, bit 1 is the first bit to betransmitted.

For fields which are contained within a single octet, the lowestnumbered bit of the field represents the least significant bit (2⁰).When a field spans multiple octets, the lowest numbered bit of the fieldin the highest numbered octet containing the field represents the leastsignificant bit (2⁰). The order of the bit values within each octetincreases as the bit number increases. The order of the bit values fromoctet to octet increases as the octet number decreases. FIG. 7illustrates a field which spans two octets.

An exception to this convention is the Frame Check Sequence (FCS) field,which spans two octets. In this case, the order of the bit values withinthe octets is reversed. That is, bit 1 of the first octet is the MSB andbit 8 of the second octet is the LSB (see FIG. 8).

Messages of the instant invention use the frame structure shown in FIG.9. Messages start and end with a standard HDLC flag octet (01111110₂),as defined in ISO/IEC 3309. The Frame Check Sequence (FCS) field isdefined in ISO/IEC 3309. Transparency using the Octet stuffing method isdefined in ISO/IEC 3309.

The message information field consists of three components; anidentification field (1), followed by a standard information field (S);and an optional non-standard information field (NS). The generalstructure of the message information field is shown in FIG. 10.

In both the identification (I) and the standard information (S) fields,most of the information to be conveyed consists of parameters relatingto particular modes, features or capabilities associated with the twostations. In order to encode these parameters in accordance with aconsistent set of rules; and allow future extension of the parameterlist in a way that permits present and future implementations of thepresent invention to correctly parse the information field, theparameters are linked together in an extensible tree structure. Theorder in which the parameters in the tree are transmitted and the use ofdelimiting bits which enable the tree to be reconstructed at thereceiver will be described in the rules set out below.

Parameters (Pars) are classified as (1) NPars—meaning, parameters whichhave no subparameters associated with them, and (2) SPars—meaningparameters which have subparameters associated with them. The generalstructure of this tree is as shown in FIG. 11. At level 1, which is thehighest level of the tree, each SPar has a series of Pars (NPars andpossibly SPars) at level 2 in the tree associated with it. Similarly, atlevel 2 in the tree, each SPar has associated with it a series of NParsat level 3 in the tree.

Parameters are binary encoded, and transmitted serially. Parameters ofthe same type (i.e., level, classification and association) aretransmitted sequentially, as a block of data consisting of an integralnumber of octets. The transmission order of NPars and SPars is specifiedin FIG. 12. {Par(2)_(n)} indicates a set of level 2 parametersassociated with the n'th level 1 SPar, and consists of NPar(2)_(n)parameters and possibly SPar(2)_(n) parameters. {NPar(3)_(n,m)}indicates a set of level 3 NPars associated with the m'th level 2 SPar,which in turn is associated with the n'th level 1 SPar. The transmissionof parameters begins with the first octet of NPar(1) and ends with thelast octet of Par(2)_(N).

The use of delimiting bits is illustrated in FIG. 12. At least one bitis defined as a delimiting bit within each octet of an informationblock. This is used to define the last octet in the block. A binary ZEROin this bit position indicates that there is at least one additionaloctet in the block. A binary ONE in this bit position indicates the lastoctet in the block.

Bit 8 is used to delimit the {NPar(1)} block, the {SPar(1)} block, andeach of the Par(2) blocks. There are “N” Par(2) blocks, one for each ofthe capabilities in the {SPar(1)} block that is enabled (e.g., set tobinary ONE).

Bit 7 is used to delimit each {NPar(2)} block, each {SPar(2)} block, andeach of the associated {NPar(3)} blocks. FIG. 12 indicates that thereare “M” NPar(3) blocks, one for each of the capabilities in the{SPar(2)_(n)} block that is enabled (e.g., set to binary ONE). “M” maybe different for each of the Par(2) blocks.

A Par(2) block may either contain both NPar(2) and SPar(2) octets, orNPar(2) octets alone. To indicate that a Par(2) block contains onlyNPar(2) octets, bits 7 and 8 are both set to binary ONE in the lastNPar(2) octet. Bits 1 through 7 at level 1 of the tree and bits 1through 6 at level 2 of the tree may be used to encode parameters. Toallow for compatibility with future revisions (developments), receiversshall parse all information blocks and ignore information that is notunderstood.

In a first embodiment, the identification field consists of threecomponents; a four-bit message type field (see Table 15), followed by afour-bit revision number field (see Table 17), followed by a bit-encodedparameter field.

In a second embodiment, the identification field consists of threecomponents; an eight-bit message type field (see Table 16), followed byan eight-bit revision number field (Table 18), followed by a bit-encodedparameter field. This general structure is shown in FIG. 13.

The message type field identifies the message type of the frame. Therevision number field identifies the revision number of the currentinvention to which the equipment conforms. The Identification fieldencompasses information including, but not limited to: (1)non-modulation specific information, (2) channel capability information,(3) data rate information, (4) data flow characteristics, and (5)splitter Information. The Identification field comprises several octetsof NPar(1)s, SPar(l)s, and NPar(2). NPar(1) and SPar(1) octets arealways transmitted. NPar(2) octets are transmitted only if thecorresponding bit in the SPar(1) is a “1”. Octets are transmitted in theorder shown in Table 19.

Vendor identification, including, for example, the country code,provider length, and provider code fields, follows the format of ITU-TRecommendation T.35 and is the same as used in the Non-standard fieldshown in FIG. 15.

TABLE 15 Message type field format Embodiment #1 Message Bit numberstype 4 3 2 1 MS 0 0 0 1 CL 0 0 1 0 CLR 0 0 1 1 ACK(1) 0 1 0 0 ACK(2) 0 10 1 Reserved for ITU-T 0 1 1 0 Reserved for ITU-T 0 1 1 1 NAK(1) 1 0 0 0NAK(2) 1 0 0 1 NAK(3) 1 0 1 0 NAK(4) 1 0 1 1 RC 1 1 0 0 Hangup 1 1 0 1Reserved for ITU-T 1 1 1 0 Reserved for ITU-T 1 1 1 1

TABLE 16 Message type field format Embodiment #2 Bit numbers Messagetype 8 7 6 5 4 3 2 1 MS 0 0 0 0 0 0 0 0 MR 0 0 0 0 0 0 0 1 CL 0 0 0 0 00 1 0 CLR 0 0 0 0 0 0 1 1 ACK(1) 0 0 0 1 0 0 0 0 ACK(2) 0 0 0 1 0 0 0 1NAK-EF 0 0 1 0 0 0 0 0 NAK-NR 0 0 1 0 0 0 0 1 NAK-NS 0 0 1 0 0 0 1 0NAK-NU 0 0 1 0 0 0 1 1 REQ-MS 0 0 1 1 0 1 0 0 REQ-MR 0 0 1 1 0 1 0 1REQ-CLR 0 0 1 1 0 1 1 1

TABLE 17 Revision Number field format Embodiment #1 Revision Bit numbersnumber 8 7 6 5 Revision 1 0 0 0 1

TABLE 18 Revision Number field format Embodiment #2 Bit numbers Revisionnumber 8 7 6 5 4 3 2 1 Revision 1 0 0 0 0 0 0 0 1

TABLE 19 Identification Field - Order of Octets N/S Name Type Table #Message type field format — Table 15/ Table 16 Version Type field —Table 17/ Table 18 Country code — Provider Length — Provider code (Loctets) — Identification field - {NPar(1)} coding NPar(1) Table 20Identification field (Capabilities Information)- SPar(1) Table 21{SPar(1)} coding - Octet 1 Identification field (Service Requests)-SPar(1) Table 22 {SPar(1)} coding - Octet 2 Identification Field - (CI)Currently transmitted NPar(2) Table 23 carriers {NPar(2)} coding - Octet1 Identification Field - (CI) Currently transmitted NPar(2) Table 24carriers {NPar(2)} coding - Octet 2 Identification field - (CI) Spectrumfirst usable NPar(2) Table 25 frequency {NPar(2)} coding Identificationfield - (CI) Spectrum maximum NPar(2) Table 26 frequency - upstream{NPar(2)} coding Identification field - (CI) Spectrum maximum NPar(2)Table 27 frequency - downstream {NPar(2)} coding Identification Field -(CI) Splitter Information NPar(2) Table 28 {NPar(2)} coding - Octet 1Identification Field - (CI) Splitter Information NPar(2) Table 29{NPar(2)} coding - Octet 2 Identification field - (SR) Data rate AmountDS NPar(2) Table 30 (Average) {NPar(2)} coding - Octet 1 Identificationfield - (SR) Data rate Amount DS NPar(2) Table 31 (Maximum) {NPar(2)}coding - Octet 2 Identification field - (SR) Data rate Amount DS NPar(2)Table 32 (Minimum) {NPar(2)} coding - Octet 3 Identification field -(SR) Data rate Amount US NPar(2) Table 30 (Average) {NPar(2)} coding -Octet 1 Identification field - (SR) Data rate Amount US NPar(2) Table 31(Maximum) {NPar(2)} coding - Octet 2 Identification field - (SR) Datarate Amount US NPar(2) Table 32 (Minimum) {NPar(2)} coding - Octet 3Identification field - (SR) Data rate type DS NPar(2) Table 33 {NPar(2)}coding Identification field - (SR) Data rate type US NPar(2) Table 33{NPar(2)} coding Identification field - (SR) Data rate type US NPar(2)Table 33 {NPar(2)} coding Identification Field - (SR) Requesttransmission NPar(2) Table 34 of carriers {NPar(2)} coding - Octet 1Identification Field - (SR) Request transmission NPar(2) Table 35 ofcarriers {NPar(2)} coding - Octet 2 CI = Capabilities Information SR =Service requirement DS = Downstream US = Upstream

The Identification (I) parameter field is composed of several octets ofNPar(1)s, SPar(1)s, and NPar(2). In the octets, each parameter isassigned a unique bit position (or field). a binary ONE in the assignedbit position indicates that the parameter is valid. The validity ofmultiple parameters is conveyed by transmitting a binary ONE in each bitposition corresponding to a valid parameter. a field is encoded asdescribed in it's table.

NPar(1) and SPar(1) octets are always transmitted. NPar(2) octets aretransmitted to only if the corresponding bit in the SPar(1) is a “1”.Octets are transmitted in the order shown in Table 19. The level 1 NParis listed in Table 20. The level 1 SPars is described in Table 21 andTable 22 The level 2 NPars are separately described in Table 23 throughTable 35.

TABLE 20 Identification field - {NPar(1)} coding SPar(1)s 8 7 6 5 4 3 21 Reserved for ITU-T x x x x x x x 1 Rec. V.8 x x x x x x 1 x Rec.V.8bis x x x x x 1 x x Additional information available x x x x 1 x x xTransmit ACK(1) x x x 1 x x x x Reserved for ITU-T x x 1 x x x x xNon-standard field x 1 x x x x x x No parameters in this octet x 0 0 0 00 0 0 NOTE .Rec. V.8 and Rec. V.8bis availability can be identitied toallow escape into voiceband modulation procedures.

TABLE 21 Identification field (Capabilities Information)- {SPar(1)}coding - Octet 1 SPar(1)s 8 7 6 5 4 3 2 1 Currently transmitted carriersx x x x x x x 1 Spectrum first usable frequency x x x x x x 1 x Spectrummaximum frequency - x x x x x 1 x x upstream Spectrum maximumfrequency - x x x x 1 x x x downstream Splitter Information - xTU-R x xx 1 x x x x Reserved for ITU-T x x 1 x x x x x non standard capabilitiesinfor- x 1 x x x x x x mation No parameters in this octet x 0 0 0 0 0 00 NOTE - .

TABLE 22 Identification field (Service Requests)- {SPar(1)} coding -Octet 2 SPar(1)s 8 7 6 5 4 3 2 1 Data rate Amount Downstream x x x x x xx 1 Data rate Amount Upstream x x x x x x 1 x Data rate Type Downstreamx x x x x 1 x x Data rate Type Upstream x x x x 1 x x x Request transmitof carriers x x x 1 x x x x Reserved for ITU-T x x 1 x x x x x nonstandard service request x 1 x x x x x x No parameters in this octet x 00 0 0 0 0 0 Transmitted carriers and families are indicated above.

TABLE 23 Identification Field - (CI) Currently transmitted carriers{NPar(2)} coding - Octet 1 NPar(2)s 8 7 6 5 4 3 2 1 Currentlytransmitting 4.3125 kHz x x x x x x x 1 family (a) Currentlytransmitting 4 kHz x x x x x x 1 x family (B) Currently transmittingcarrier x x x x x 1 x x A_(01-X) Currently transmitting carrier x x x x1 x x x A_(02-X) Currently transmitting carrier x x x 1 x x x x A_(03-X)Currently transmitting carrier x x 1 x x x x x A_(04-X) No parameters inthis octet x x 0 0 0 0 0 0

TABLE 24 Identification Field - (CI) Currently transmitted carriers{NPar(2)} coding - Octet 2 NPar(2)s 8 7 6 5 4 3 2 1 Currentlytransmitting carrier A_(05-X) x x x x x x x 1 Currently transmittingcarrier A_(06-X) x x x x x x 1 x Currently transmitting carrier A_(07-X)x x x x x 1 x x Currently transmitting carrier A_(08-X) x x x x 1 x x xCurrently transmitting carrier B_(01-X) x x x 1 x x x x Currentlytransmitting carrier B_(02-X) x x 1 x x x x x No parameters in thisoctet x x 0 0 0 0 0 0

The usable spectrum frequencies of Tables 25-27) are useful to indicatethe TX/RX capabilities of the xTU-x (such as, for example, an xTU-C thatonly transmits through tone 68) and can indicate FDM vs. overlappedspectrum operation availability.

TABLE 25 Identification field - (CI) Spectrum first usable frequency{NPar(2)} coding NPar(2)s 8 7 6 5 4 3 2 1 Reserved for ITU-T x x 1 1 1 11 1 Unspecified by terminal x x 0 0 0 0 0 0 Spectrum first usablefrequency x x x x x x x x (bits 6-1 × 10 KHz)

TABLE 26 Identification field - (CI) Spectrum maximum frequency -upstream {NPar(2)} coding NPar(2)s 8 7 6 5 4 3 2 1 Reserved for ITU-T xx 1 1 1 1 1 1 Unspecified by terminal x x 0 0 0 0 0 0 spectrum maximumfrequency - x x 1 x x x x x upstream (bits 5-1 × 1 MHZ) spectrum maximumfrequency - x x 0 x x x x x upstream (bits 5-1 × 10 KHZ)

TABLE 27 Identification field - {CI) Spectrum maximum frequency -downstream {NPar(2)} coding NPar(2)s 8 7 6 5 4 3 2 1 Reserved for ITU-Tx x 1 1 1 1 1 1 Unspecified by terminal x x 0 0 0 0 0 0 spectrum maximumfrequency - x x 1 x x x x x downstream (bits 5-1 × 1 MHZ) spectrummaximum frequency - x x 0 x x x x x downstream (bits 5-1 × 10 KHZ)

TABLE 28 Identification Field - (CI) Splitter Information {NPar(2)}coding - Octet 1 NPar(2)s 8 7 6 5 4 3 2 1 LPF is voice x x x x x x x 1LPF is USA ISDN x x x x x x 1 x LPF is European ISDN x x x x x 1 x xReserved for ITU-T x x x x 1 x x x Reserved for ITU-T x x x 1 x x x xNon-standard LPF x x 1 x x x x x No parameters in this octet x x 0 0 0 00 0

TABLE 29 Identification Field - (CI) Splitter Information {NPar(2)}coding - Octet 2 NPar(2)s 8 7 6 5 4 3 2 1 HPF is 25 kHz ( voice) x x x xx x x 1 HPF is 90 kHz USA ISDN x x x x x x 1 x HPF is 150 kHz (ADSL withx x x x x 1 x x European ISDN) HPF is 300 kHz (VDSL) x x x x 1 x x xReserved for ITU-T x x x 1 x x x x Non-standard HPF x x 1 x x x x x Noparameters in this octet x x 0 0 0 0 0 0

TABLE 30 Identification field - (SR) Data Rate Amount (Average){NPar(2)} coding - Octet 1 NPar(2)s 8 7 6 5 4 3 2 1 Reserved for ITU-T xx 1 1 1 1 1 1 Unspecified by terminal x x 0 0 0 0 0 0 Average bandwidth(bits 5-1 × 512 x x 1 x x x x x kbps) Average bandwidth (bits 5-1 × 32 xx 0 x x x x x kbps)

TABLE 31 Identification field - (SR) Data Rate Amount (Maximum){NPar(2)} coding - Octet 2 NPar(2)s 8 7 6 5 4 3 2 1 Reserved for ITU-T xx 1 1 1 1 1 1 Unspecified by terminal x x 0 0 0 0 0 0 Maximum bandwidth(bits 5-1 × x x 1 x x x x x 512 kbps) Maximum bandwidth (bits 5-1 × x x0 x x x x x 32 kbps

TABLE 32 Identification field - (SR) Data Rate Amount (Minimum){NPar(2)} coding - Octet 3 NPar(2)s 8 7 6 5 4 3 2 1 Reserved for ITU-T xx 1 1 1 1 1 1 Unspecified by terminal x x 0 0 0 0 0 0 Minimum bandwidth(bits 5-1 × x x 1 x x x x x 512 kbps) Minimum bandwidth (bits 5-1 × x x0 x x x x x 32 kbps

TABLE 33 Identification field - (SR) Data rate type {NPar(2)} codingNPar(2)s 8 7 6 5 4 3 2 1 Low latency x x x x x x x 1 Constant latency xx x x x x 1 x Bursty x x x x x 1 x x etc x x x x 1 x x x x x x 1 x x x xx x 1 x x x x x No parameters in this octet x x 0 0 0 0 0 0An xTU-X may request that the other xTU-X transmit only on a certainnumber of carriers. This permits a reduction in the number of carriersfor the rest of the transaction, or for the next initialization, asdescribed above. Note that an xTU-X should only send a request that itknows the other xTU-X can fulfill.

TABLE 34 Identification Field - (SR) Request Transmission of Carriers{NPar(2)} coding - Octet 1 NPar(2)s 8 7 6 5 4 3 2 1 Request transmitusing 4.3125 kHz x x x x x x x 1 family (A) Request transmit using 4 kHzx x x x x x 1 x family (B) Request transmit on carrier A_(01-X) x x x xx 1 x x Request transmit on carrier A_(02-X) x x x x 1 x x x Requesttransmit on carrier A_(03-X) x x x 1 x x x x Request transmit on carrierA_(04-X) x x 1 x x x x x No parameters in this octet x x 0 0 0 0 0 0

TABLE 35 Identification Field - (SR) Request Transmission of Carriers{NPar(2)} coding - Octet 2 NPar(2)s 8 7 6 5 4 3 2 1 Request transmit oncarrier A_(05-X) x x x x x x x 1 Request transmit on carrier A_(06-X) xx x x x x 1 x Request transmit on carrier A_(07-X) x x x x x 1 x xRequest transmit on carrier A_(08-X) x x x x 1 x x x Request transmit oncarrier B_(01-X) x x x 1 x x x x Request transmit on carrier B_(02-X) xx 1 x x x x x No parameters in this octet x x 0 0 0 0 0 0

The Standard Information field is composed of several octets ofNPar(1)'s, SPar(1)'s, and possibly NPar(2), SPar(2), and SPar(3).NPar(1) and SPar(1) octets are specified herein and are alwaystransmitted. NPar(1) octet encoding is described in Table 36, whileSPar(1) octets encoding is described in Tables 37 and 38.

The contents of NPar(2), SPar(2), and SPar(3) octets are transmittedonly if the corresponding bit in SPar(1) is a “1”. In general, thecontents regard modulation and protocol details specific to respectiveITU-T Recommendations. Some illustrative specifications of modulationencoding are given in Tables 39-45.

TABLE 36 Standard Information field - {NPar(1)} coding SPar(1)s 8 7 6 54 3 2 1 Voiceband (Rec. V.8 or V.8bis) x x x x x x x 1 G.997.1 (clearEOC) channel using x x x x x x 1 x present invention Reserved for ITU-Tx x x x x 1 x x Reserved for ITU-T x x x x 1 x x x Reserved for ITU-T xx x 1 x x x x Reserved for ITU-T x x 1 x x x x x Reserved for ITU-T x 1x x x x x x No parameters in this octet x 0 0 0 0 0 0 0

TABLE 37 Standard Information field - {SPar(1)} coding - Octet 1SPar(1)s 8 7 6 5 4 3 2 1 G.992.1 - Annex A x x x x x x x 1 G.992.1 -Annex B x x x x x x 1 x G.992.1 - Annex C x x x x x 1 x x G.hdsl x x x x1 x x x G.992.2 x x x 1 x x x x G.992.2 - (in TCM-ISDN x x 1 x x x x xenvironment) Non-standard capabilities (modu- x 1 x x x x x x lations)No parameters in this octet x 0 0 0 0 0 0 0

TABLE 38 Standard Information field - {SPar(1)} coding - Octet 2SPar(1)s 8 7 6 5 4 3 2 1 ANSI HDSL2 / G.hdsl2 x x x x x x x 1 ANSI VDSLa / G.vdsl Annex a x x x x x x 1 x ANSI VDSL B / G.vdsl Annex B x x x xx 1 x x ANSI T1.413 Issue 2 x x x x 1 x x x Reserved for ITU-T x x x 1 xx x x Reserved for ITU-T x x 1 x x x x x Reserved for ITU-T x 1 x x x xx x No parameters in this octet x 0 0 0 0 0 0 0

TABLE 39 Modulation - G.992.1 Annex a {NPar(2)} coding - Octet 1NPar(2)s 8 7 6 5 4 3 2 1 Specify parameters or profiles for x x x x x xx 1 G.992.1 Annex a x x x x x x 1 x STM=0, ATM=1 x x x x x 1 x x NTR x xx x 1 x x x etc x x x 1 x x x x x x 1 x x x x x No parameters in thisoctet x x 0 0 0 0 0 0

TABLE 40 Modulation - G.992.1 Annex a {NPar(2)} coding - Octet 2NPar(2)s 8 7 6 5 4 3 2 1 AS1 / ATM1 downstream x x x x x x x 1 AS2downstream x x x x x x 1 x AS3 downstream x x x x x 1 x x LS1 downstreamx x x x 1 x x x LS2 downstream x x x 1 x x x x LS1 / ATM1 upstream x x 1x x x x x No parameters in this octet x x 0 0 0 0 0 0

TABLE 41 Modulation - G.992.1 Annex a {NPar(2)} coding - Octet 3NPar(2)s 8 7 6 5 4 3 2 1 LS2 upstream x x x x x x x 1 x x x x x x 1 x xx x x x 1 x x x x x x 1 x x x x x x 1 x x x x x x 1 x x x x x Noparameters in this octet x x 0 0 0 0 0 0

TABLE 42 Modulation - G.992.1 Annex B {NPar(2)} coding - Octet 1NPar(2)s 8 7 6 5 4 3 2 1 0= Tones above 32 / 1 = Tones x x x x x x x 1below 33 allowed - NOTE x x x x x x 1 x x x x x x 1 x x etc x x x x 1 xx x x x x 1 x x x x x x 1 x x x x x No parameters in this octet x x 0 00 0 0 0 NOTE When the message is sent by the ATU-C, it indicates itability to receive tones (0 =RX Tones above 32 / 1 = RX Tones below 33allowed): When sent by the ATU-C, it indicates the ability to transmittones. (0 =only TX Tones above 32 / 1 = RX Tones 33 to 63 mandatory, RXtones 1 to 32 optional)

TABLE 43 Modulation - G.992.1 Annex C {NPar(2)} coding - Octet 1NPar(2)s 8 7 6 5 4 3 2 1 Specify parameters or profiles for x x x x x xx 1 G.992.1 Annex C x x x x x x 1 x x x x x x 1 x x etc x x x x 1 x x xx x x 1 x x x x x x 1 x x x x x No parameters in this octet x x 0 0 0 00 0

TABLE 44 Modulation - G.hdsl {NPar(2)} coding NPar(2)s 8 7 6 5 4 3 2 1Use G.hdsl Annex B x x x x x x x 1 x x x x x x 1 x x x x x x 1 x x etc xx x x 1 x x x x x x 1 x x x x x x 1 x x x x x No parameters in thisoctet x x 0 0 0 0 0 0

TABLE 45 Modulation - G.992.2 {NPar(2)} coding - Octet 1 NPar(2)s 8 7 65 4 3 2 1 Specify parameters or profiles for x x x x x x x 1 G.992.2 x xx x x x 1 x etc x x x x x 1 x x x x x x 1 x x x x x x 1 x x x x x x 1 xx x x x No parameters in this octet x x 0 0 0 0 0 0

The MS, CL, and CLR messages may optionally contain a non-standardinformation field to convey information beyond that defined herein. Whennon-standard information is to be sent, the “Non-standard field”parameter is set to binary ONE in the identification field of thetransmitted message. The non-standard information field may optionallybe composed of one or more non-standard information blocks (see FIG.14).

Each non-standard information block (see FIG. 15) comprises: (1) alength indicator (one octet) that specifies the length of the remainderof the block; (2) a country code (K octets), as defined inRecommendation T.35; (3) a length indicator (one octet), that specifiesthe length of the provider code(e.g., the value in octets indicatingthat L octets follow); (4) a provider code as specified by the countryidentified in Recommendation T.35; and (5) non-standard information (Moctets).

The present invention permits the modulation used by the presentinvention to continue to be transmitted after the negotiation proceduresare complete. According to a feature of the present invention, themodulation can be used as, for example, a clear channel EOC. Forexample, a standard information NPar(1) bit indicates the availabilityof CL/CLR messages, and the same bit is used to indicate selection in MSmessages. Following the termination of the present invention negotiationprotocol with the ACK message, the carrier could remain ON to provide aclear EOC channel.

In the past, the configuration of an ATU-R Handshake by a Terminal wasperformed using either AT commands, or other proprietary means.According to the instant invention, an AOM management protocol is usedbetween a Terminal and the ATU-R, and a similar communication pathbetween the ATU-C and the network management systems. In the preferredembodiments, the Terminal uses the SNMP protocol (IETF RFC 1157published May 1990) to configure and monitor the present invention'shandshake procedure in an ATU-R. Since the present invention's handshakeprocedure data rate is under 100 bytes/sec, a reasonable time needs tobe provided for the Terminal to actively participate in the handshakesession.

In general, the CL and CLR message parameters can be set before thehandshake procedure begins. The present invention enables the Terminalto inquire (of the ATU-R) the status of several of the parameters.

SNMP Traps can be used to indicate critical parts of the receivedmessages that must be acted on by the Terminal if it desires toinfluence items, such as, for example, MS or ACK/NAK messages.

While the invention has been particularly shown and described withreference to the preferred embodiments thereof, it is understood bythose skilled in the art that various alterations in form and/or detailmay may be made without departing from the spirit and/or scope of theinvention, as defined by the following claims. Although the inventionhas been described with reference to the particular means, materials andembodiments, it is to be understood that the invention is not limited tothe particulars disclosed herein, but extends to all equivalents withinthe scope of the claims.

1. An apparatus for establishing a communication link, comprising: anegotiation data transmitter, associated with an initiatingcommunication device, that transmits at least one carrier includingfirst negotiation information bits representing a first list of xDSLmodulation transmission protocol capabilities to a respondingcommunication device; a negotiation data receiver, associated with theinitiating communication device, that receives at least one carrierincluding second negotiation information bits representing a second listof xDSL modulation transmission protocol capabilities of the respondingcommunication device, in response to said transmitted at least onecarrier; and a selector that selects an xDSL modulation transmissionprotocol common to said first list of xDSL modulation transmissionprotocol capabilities and the second list of xDSL modulationtransmission protocol capabilities in accordance with the respondingcommunication device to establish a communication channel, wherein saidtransmitted at least one carrier contains data related to a useablefrequency spectrum carrier allocation, said transmission of said firstnegotiation information bits and said reception of said secondnegotiation information bits occurring prior to an initializationprocedure to establish the communication link.
 2. An apparatus forestablishing a communication link, comprising: a negotiation datatransmitter, associated with an initiating communication device, thattransmits at least one carrier including first negotiation informationbits representing a first list of xDSL modulation transmission protocolcapabilities to a responding communication device; a negotiation datareceiver, associated with the initiating communication device, thatreceives at least one carrier including second negotiation informationbits representing a second list of xDSL modulation transmission protocolcapabilities of the responding communication device, in response to saidtransmitted at least one carrier; and a selector that selects an xDSLmodulation transmission protocol common to said first list of xDSLmodulation transmission protocol capabilities and the second list ofxDSL modulation transmission protocol capabilities in accordance withthe responding communication device to establish a communicationchannel, wherein said negotiation data transmitter transmits said atleast one carrier in accordance with neighboring receiving systems, saidtransmission of said first negotiation information bits and saidreception of said second negotiation information bits occurring prior toan initialization procedure to establish the communication link.
 3. Theapparatus of claim 2, wherein transmission characteristics of saidtransmitted at least one carrier is re-configurable during atransmission operation in order to minimize interference with theneighboring receiving systems.
 4. A method for establishing acommunication link, comprising: transmitting at least one carrier thatincludes first negotiation information bits representing a first list ofxDSL modulation transmission protocol capabilities to a respondingcommunication device; receiving at least one carrier that includessecond negotiation information bits representing a second list of xDSLmodulation transmission protocol capabilities of the respondingcommunication device, in response to the transmitted at least onecarrier; and selecting an xDSL modulation transmission protocol commonto the first list of xDSL modulation transmission protocol capabilitiesand the second list of xDSL modulation transmission protocolcapabilities in accordance with the received at least one carrier toestablish a communication channel, wherein the transmitted at least onecarrier comprises transmitting the at least one carrier in accordancewith neighboring receiving systems, the transmission of the firstnegotiation information bits and the reception of the second negotiationinformation bits occurring prior to an initialization procedure toestablish the communication link.
 5. The method of claim 4, furthercomprising reconfiguring the transmitted at least one carrier tominimize interference with the neighboring receiving systems.
 6. Themethod of claim 4, further comprising transmitting the at least onecarrier with data related to a useable frequency spectrum carrierallocation.
 7. An apparatus for establishing a communication link,comprising: a negotiation data transmitter, associated with aninitiating communication device, that transmits first negotiationinformation bits representing a first list of xDSL modulationtransmission protocol capabilities to a responding communication device;a negotiation data receiver, associated with the initiatingcommunication device, that receives second negotiation information bitsrepresenting a second list of xDSL modulation transmission protocolcapabilities of the responding communication device, in response to saidtransmitted first negotiation information bits; and a selector thatselects an xDSL modulation transmission protocol common to said firstlist of xDSL modulation transmission protocol capabilities and thesecond list of xDSL modulation transmission protocol capabilities inaccordance with the responding communication device to establish acommunication channel, wherein said transmission of said firstnegotiation information bits and said reception of said secondnegotiation information bits occurs prior to an initialization procedureto establish the communication link.